Python2/PyMuPDF: mupdf-source/thirdparty/libjpeg/libjpeg.txt annotate

annotate mupdf-source/thirdparty/libjpeg/libjpeg.txt @ 46:7ee69f120f19 default tip

>>>>> tag v1.26.5+1 for changeset b74429b0f5c4

author	Franz Glasner <fzglas.hg@dom66.de>
date	Sat, 11 Oct 2025 17:17:30 +0200
parents	b50eed0cc0ef
children

rev	line source
2 b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1 USING THE IJG JPEG LIBRARY
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3 Copyright (C) 1994-2023, Thomas G. Lane, Guido Vollbeding.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	4 This file is part of the Independent JPEG Group's software.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	5 For conditions of distribution and use, see the accompanying README file.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	6
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	7
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	8 This file describes how to use the IJG JPEG library within an application
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	9 program. Read it if you want to write a program that uses the library.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	10
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	11 The file example.c provides heavily commented skeleton code for calling the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	12 JPEG library. Also see jpeglib.h (the include file to be used by application
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	13 programs) for full details about data structures and function parameter lists.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	14 The library source code, of course, is the ultimate reference.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	15
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	16 Note that there have been major changes from the application interface
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	17 presented by IJG version 4 and earlier versions. The old design had several
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	18 inherent limitations, and it had accumulated a lot of cruft as we added
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	19 features while trying to minimize application-interface changes. We have
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	20 sacrificed backward compatibility in the version 5 rewrite, but we think the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	21 improvements justify this.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	22
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	23
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	24 TABLE OF CONTENTS
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	25 -----------------
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	26
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	27 Overview:
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	28 Functions provided by the library
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	29 Outline of typical usage
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	30 Basic library usage:
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	31 Data formats
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	32 Compression details
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	33 Decompression details
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	34 Mechanics of usage: include files, linking, etc
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	35 Advanced features:
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	36 Compression parameter selection
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	37 Decompression parameter selection
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	38 Special color spaces
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	39 Error handling
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	40 Compressed data handling (source and destination managers)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	41 I/O suspension
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	42 Progressive JPEG support
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	43 Buffered-image mode
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	44 Abbreviated datastreams and multiple images
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	45 Special markers
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	46 Raw (downsampled) image data
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	47 Really raw data: DCT coefficients
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	48 Progress monitoring
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	49 Memory management
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	50 Memory usage
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	51 Library compile-time options
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	52 Portability considerations
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	53 Notes for MS-DOS implementors
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	54
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	55 You should read at least the overview and basic usage sections before trying
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	56 to program with the library. The sections on advanced features can be read
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	57 if and when you need them.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	58
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	59
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	60 OVERVIEW
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	61 ========
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	62
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	63 Functions provided by the library
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	64 ---------------------------------
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	65
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	66 The IJG JPEG library provides C code to read and write JPEG-compressed image
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	67 files. The surrounding application program receives or supplies image data a
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	68 scanline at a time, using a straightforward uncompressed image format. All
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	69 details of color conversion and other preprocessing/postprocessing can be
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	70 handled by the library.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	71
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	72 The library includes a substantial amount of code that is not covered by the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	73 JPEG standard but is necessary for typical applications of JPEG. These
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	74 functions preprocess the image before JPEG compression or postprocess it after
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	75 decompression. They include colorspace conversion, downsampling/upsampling,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	76 and color quantization. The application indirectly selects use of this code
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	77 by specifying the format in which it wishes to supply or receive image data.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	78 For example, if colormapped output is requested, then the decompression
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	79 library automatically invokes color quantization.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	80
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	81 A wide range of quality vs. speed tradeoffs are possible in JPEG processing,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	82 and even more so in decompression postprocessing. The decompression library
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	83 provides multiple implementations that cover most of the useful tradeoffs,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	84 ranging from very-high-quality down to fast-preview operation. On the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	85 compression side we have generally not provided low-quality choices, since
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	86 compression is normally less time-critical. It should be understood that the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	87 low-quality modes may not meet the JPEG standard's accuracy requirements;
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	88 nonetheless, they are useful for viewers.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	89
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	90 A word about functions not provided by the library. We handle a subset of
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	91 the ISO JPEG standard; most baseline, extended-sequential, and progressive
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	92 JPEG processes are supported. (Our subset includes all features now in common
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	93 use.) Unsupported ISO options include:
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	94 * Hierarchical storage
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	95 * Lossless JPEG
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	96 * DNL marker
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	97 * Nonintegral subsampling ratios
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	98 We support 8-bit to 12-bit data precision, but this is a compile-time choice
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	99 rather than a run-time choice; hence it is difficult to use different
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	100 precisions in a single application.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	101
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	102 By itself, the library handles only interchange JPEG datastreams --- in
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	103 particular the widely used JFIF file format. The library can be used by
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	104 surrounding code to process interchange or abbreviated JPEG datastreams that
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	105 are embedded in more complex file formats. (For example, this library is
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	106 used by the free LIBTIFF library to support JPEG compression in TIFF.)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	107
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	108
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	109 Outline of typical usage
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	110 ------------------------
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	111
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	112 The rough outline of a JPEG compression operation is:
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	113
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	114 Allocate and initialize a JPEG compression object
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	115 Specify the destination for the compressed data (eg, a file)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	116 Set parameters for compression, including image size & colorspace
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	117 jpeg_start_compress(...);
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	118 while (scan lines remain to be written)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	119 jpeg_write_scanlines(...);
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	120 jpeg_finish_compress(...);
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	121 Release the JPEG compression object
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	122
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	123 A JPEG compression object holds parameters and working state for the JPEG
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	124 library. We make creation/destruction of the object separate from starting
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	125 or finishing compression of an image; the same object can be re-used for a
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	126 series of image compression operations. This makes it easy to re-use the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	127 same parameter settings for a sequence of images. Re-use of a JPEG object
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	128 also has important implications for processing abbreviated JPEG datastreams,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	129 as discussed later.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	130
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	131 The image data to be compressed is supplied to jpeg_write_scanlines() from
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	132 in-memory buffers. If the application is doing file-to-file compression,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	133 reading image data from the source file is the application's responsibility.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	134 The library emits compressed data by calling a "data destination manager",
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	135 which typically will write the data into a file; but the application can
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	136 provide its own destination manager to do something else.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	137
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	138 Similarly, the rough outline of a JPEG decompression operation is:
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	139
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	140 Allocate and initialize a JPEG decompression object
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	141 Specify the source of the compressed data (eg, a file)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	142 Call jpeg_read_header() to obtain image info
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	143 Set parameters for decompression
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	144 jpeg_start_decompress(...);
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	145 while (scan lines remain to be read)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	146 jpeg_read_scanlines(...);
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	147 jpeg_finish_decompress(...);
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	148 Release the JPEG decompression object
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	149
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	150 This is comparable to the compression outline except that reading the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	151 datastream header is a separate step. This is helpful because information
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	152 about the image's size, colorspace, etc is available when the application
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	153 selects decompression parameters. For example, the application can choose an
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	154 output scaling ratio that will fit the image into the available screen size.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	155
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	156 The decompression library obtains compressed data by calling a data source
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	157 manager, which typically will read the data from a file; but other behaviors
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	158 can be obtained with a custom source manager. Decompressed data is delivered
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	159 into in-memory buffers passed to jpeg_read_scanlines().
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	160
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	161 It is possible to abort an incomplete compression or decompression operation
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	162 by calling jpeg_abort(); or, if you do not need to retain the JPEG object,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	163 simply release it by calling jpeg_destroy().
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	164
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	165 JPEG compression and decompression objects are two separate struct types.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	166 However, they share some common fields, and certain routines such as
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	167 jpeg_destroy() can work on either type of object.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	168
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	169 The JPEG library has no static variables: all state is in the compression
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	170 or decompression object. Therefore it is possible to process multiple
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	171 compression and decompression operations concurrently, using multiple JPEG
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	172 objects.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	173
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	174 Both compression and decompression can be done in an incremental memory-to-
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	175 memory fashion, if suitable source/destination managers are used. See the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	176 section on "I/O suspension" for more details.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	177
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	178
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	179 BASIC LIBRARY USAGE
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	180 ===================
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	181
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	182 Data formats
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	183 ------------
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	184
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	185 Before diving into procedural details, it is helpful to understand the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	186 image data format that the JPEG library expects or returns.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	187
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	188 The standard input image format is a rectangular array of pixels, with each
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	189 pixel having the same number of "component" or "sample" values (color
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	190 channels). You must specify how many components there are and the colorspace
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	191 interpretation of the components. Most applications will use RGB data
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	192 (three components per pixel) or grayscale data (one component per pixel).
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	193 PLEASE NOTE THAT RGB DATA IS THREE SAMPLES PER PIXEL, GRAYSCALE ONLY ONE.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	194 A remarkable number of people manage to miss this, only to find that their
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	195 programs don't work with grayscale JPEG files.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	196
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	197 There is no provision for colormapped input. JPEG files are always full-color
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	198 or full grayscale (or sometimes another colorspace such as CMYK). You can
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	199 feed in a colormapped image by expanding it to full-color format. However
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	200 JPEG often doesn't work very well with source data that has been colormapped,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	201 because of dithering noise. This is discussed in more detail in the JPEG FAQ
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	202 and the other references mentioned in the README file.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	203
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	204 Pixels are stored by scanlines, with each scanline running from left to
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	205 right. The component values for each pixel are adjacent in the row; for
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	206 example, R,G,B,R,G,B,R,G,B,... for 24-bit RGB color. Each scanline is an
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	207 array of data type JSAMPLE --- which is typically "unsigned char", unless
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	208 you've changed jmorecfg.h. (You can also change the RGB pixel layout, say
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	209 to B,G,R order, by modifying jmorecfg.h. But see the restrictions listed in
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	210 that file before doing so.)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	211
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	212 A 2-D array of pixels is formed by making a list of pointers to the starts of
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	213 scanlines; so the scanlines need not be physically adjacent in memory. Even
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	214 if you process just one scanline at a time, you must make a one-element
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	215 pointer array to conform to this structure. Pointers to JSAMPLE rows are of
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	216 type JSAMPROW, and the pointer to the pointer array is of type JSAMPARRAY.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	217
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	218 The library accepts or supplies one or more complete scanlines per call.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	219 It is not possible to process part of a row at a time. Scanlines are always
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	220 processed top-to-bottom. You can process an entire image in one call if you
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	221 have it all in memory, but usually it's simplest to process one scanline at
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	222 a time.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	223
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	224 For best results, source data values should have the precision specified by
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	225 BITS_IN_JSAMPLE (normally 8 bits). For instance, if you choose to compress
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	226 data that's only 6 bits/channel, you should left-justify each value in a
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	227 byte before passing it to the compressor. If you need to compress data
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	228 that has more than 8 bits/channel, compile with BITS_IN_JSAMPLE = 9 to 12.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	229 (See "Library compile-time options", later.)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	230
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	231
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	232 The data format returned by the decompressor is the same in all details,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	233 except that colormapped output is supported. (Again, a JPEG file is never
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	234 colormapped. But you can ask the decompressor to perform on-the-fly color
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	235 quantization to deliver colormapped output.) If you request colormapped
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	236 output then the returned data array contains a single JSAMPLE per pixel;
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	237 its value is an index into a color map. The color map is represented as
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	238 a 2-D JSAMPARRAY in which each row holds the values of one color component,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	239 that is, colormap[i][j] is the value of the i'th color component for pixel
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	240 value (map index) j. Note that since the colormap indexes are stored in
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	241 JSAMPLEs, the maximum number of colors is limited by the size of JSAMPLE
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	242 (ie, at most 256 colors for an 8-bit JPEG library).
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	243
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	244
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	245 Compression details
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	246 -------------------
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	247
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	248 Here we revisit the JPEG compression outline given in the overview.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	249
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	250 1. Allocate and initialize a JPEG compression object.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	251
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	252 A JPEG compression object is a "struct jpeg_compress_struct". (It also has
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	253 a bunch of subsidiary structures which are allocated via malloc(), but the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	254 application doesn't control those directly.) This struct can be just a local
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	255 variable in the calling routine, if a single routine is going to execute the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	256 whole JPEG compression sequence. Otherwise it can be static or allocated
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	257 from malloc().
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	258
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	259 You will also need a structure representing a JPEG error handler. The part
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	260 of this that the library cares about is a "struct jpeg_error_mgr". If you
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	261 are providing your own error handler, you'll typically want to embed the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	262 jpeg_error_mgr struct in a larger structure; this is discussed later under
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	263 "Error handling". For now we'll assume you are just using the default error
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	264 handler. The default error handler will print JPEG error/warning messages
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	265 on stderr, and it will call exit() if a fatal error occurs.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	266
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	267 You must initialize the error handler structure, store a pointer to it into
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	268 the JPEG object's "err" field, and then call jpeg_create_compress() to
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	269 initialize the rest of the JPEG object.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	270
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	271 Typical code for this step, if you are using the default error handler, is
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	272
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	273 struct jpeg_compress_struct cinfo;
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	274 struct jpeg_error_mgr jerr;
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	275 ...
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	276 cinfo.err = jpeg_std_error(&jerr);
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	277 jpeg_create_compress(&cinfo);
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	278
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	279 jpeg_create_compress allocates a small amount of memory, so it could fail
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	280 if you are out of memory. In that case it will exit via the error handler;
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	281 that's why the error handler must be initialized first.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	282
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	283
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	284 2. Specify the destination for the compressed data (eg, a file).
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	285
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	286 As previously mentioned, the JPEG library delivers compressed data to a
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	287 "data destination" module. The library includes one data destination
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	288 module which knows how to write to memory or to a file (or any stdio stream).
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	289 You can use your own destination module if you want to do something else,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	290 as discussed later.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	291
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	292 If you use the standard destination module, you must open the target stdio
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	293 stream beforehand. Typical code for this step looks like:
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	294
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	295 FILE * outfile;
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	296 ...
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	297 if ((outfile = fopen(filename, "wb")) == NULL) {
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	298 fprintf(stderr, "can't open %s\n", filename);
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	299 exit(1);
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	300 }
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	301 jpeg_stdio_dest(&cinfo, outfile);
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	302
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	303 where the last line invokes the standard destination module.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	304
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	305 WARNING: it is critical that the binary compressed data be delivered to the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	306 output file unchanged. On non-Unix systems the stdio library may perform
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	307 newline translation or otherwise corrupt binary data. To suppress this
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	308 behavior, you may need to use a "b" option to fopen (as shown above), or use
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	309 setmode() or another routine to put the stdio stream in binary mode. See
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	310 cjpeg.c and djpeg.c for code that has been found to work on many systems.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	311
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	312 You can select the data destination after setting other parameters (step 3),
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	313 if that's more convenient. You may not change the destination between
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	314 calling jpeg_start_compress() and jpeg_finish_compress().
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	315
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	316
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	317 3. Set parameters for compression, including image size & colorspace.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	318
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	319 You must supply information about the source image by setting the following
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	320 fields in the JPEG object (cinfo structure):
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	321
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	322 image_width Width of image, in pixels
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	323 image_height Height of image, in pixels
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	324 input_components Number of color channels (samples per pixel)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	325 in_color_space Color space of source image
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	326
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	327 The image dimensions are, hopefully, obvious. JPEG supports image dimensions
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	328 of 1 to 64K pixels in either direction. The input color space is typically
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	329 RGB or grayscale, and input_components is 3 or 1 accordingly. (See "Special
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	330 color spaces", later, for more info.) The in_color_space field must be
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	331 assigned one of the J_COLOR_SPACE enum constants, typically JCS_RGB or
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	332 JCS_GRAYSCALE.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	333
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	334 JPEG has a large number of compression parameters that determine how the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	335 image is encoded. Most applications don't need or want to know about all
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	336 these parameters. You can set all the parameters to reasonable defaults by
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	337 calling jpeg_set_defaults(); then, if there are particular values you want
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	338 to change, you can do so after that. The "Compression parameter selection"
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	339 section tells about all the parameters.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	340
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	341 You must set in_color_space correctly before calling jpeg_set_defaults(),
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	342 because the defaults depend on the source image colorspace. However the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	343 other three source image parameters need not be valid until you call
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	344 jpeg_start_compress(). There's no harm in calling jpeg_set_defaults() more
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	345 than once, if that happens to be convenient.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	346
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	347 Typical code for a 24-bit RGB source image is
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	348
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	349 cinfo.image_width = Width; /* image width and height, in pixels */
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	350 cinfo.image_height = Height;
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	351 cinfo.input_components = 3; /* # of color components per pixel */
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	352 cinfo.in_color_space = JCS_RGB; /* colorspace of input image */
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	353
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	354 jpeg_set_defaults(&cinfo);
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	355 /* Make optional parameter settings here */
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	356
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	357
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	358 4. jpeg_start_compress(...);
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	359
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	360 After you have established the data destination and set all the necessary
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	361 source image info and other parameters, call jpeg_start_compress() to begin
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	362 a compression cycle. This will initialize internal state, allocate working
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	363 storage, and emit the first few bytes of the JPEG datastream header.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	364
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	365 Typical code:
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	366
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	367 jpeg_start_compress(&cinfo, TRUE);
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	368
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	369 The "TRUE" parameter ensures that a complete JPEG interchange datastream
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	370 will be written. This is appropriate in most cases. If you think you might
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	371 want to use an abbreviated datastream, read the section on abbreviated
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	372 datastreams, below.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	373
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	374 Once you have called jpeg_start_compress(), you may not alter any JPEG
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	375 parameters or other fields of the JPEG object until you have completed
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	376 the compression cycle.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	377
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	378
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	379 5. while (scan lines remain to be written)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	380 jpeg_write_scanlines(...);
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	381
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	382 Now write all the required image data by calling jpeg_write_scanlines()
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	383 one or more times. You can pass one or more scanlines in each call, up
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	384 to the total image height. In most applications it is convenient to pass
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	385 just one or a few scanlines at a time. The expected format for the passed
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	386 data is discussed under "Data formats", above.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	387
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	388 Image data should be written in top-to-bottom scanline order. The JPEG spec
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	389 contains some weasel wording about how top and bottom are application-defined
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	390 terms (a curious interpretation of the English language...) but if you want
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	391 your files to be compatible with everyone else's, you WILL use top-to-bottom
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	392 order. If the source data must be read in bottom-to-top order, you can use
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	393 the JPEG library's virtual array mechanism to invert the data efficiently.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	394 Examples of this can be found in the sample application cjpeg.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	395
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	396 The library maintains a count of the number of scanlines written so far
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	397 in the next_scanline field of the JPEG object. Usually you can just use
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	398 this variable as the loop counter, so that the loop test looks like
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	399 "while (cinfo.next_scanline < cinfo.image_height)".
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	400
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	401 Code for this step depends heavily on the way that you store the source data.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	402 example.c shows the following code for the case of a full-size 2-D source
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	403 array containing 3-byte RGB pixels:
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	404
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	405 JSAMPROW row_pointer[1]; /* pointer to a single row */
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	406 int row_stride; /* physical row width in buffer */
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	407
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	408 row_stride = image_width * 3; /* JSAMPLEs per row in image_buffer */
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	409
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	410 while (cinfo.next_scanline < cinfo.image_height) {
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	411 row_pointer[0] = & image_buffer[cinfo.next_scanline * row_stride];
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	412 jpeg_write_scanlines(&cinfo, row_pointer, 1);
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	413 }
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	414
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	415 jpeg_write_scanlines() returns the number of scanlines actually written.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	416 This will normally be equal to the number passed in, so you can usually
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	417 ignore the return value. It is different in just two cases:
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	418 * If you try to write more scanlines than the declared image height,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	419 the additional scanlines are ignored.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	420 * If you use a suspending data destination manager, output buffer overrun
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	421 will cause the compressor to return before accepting all the passed lines.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	422 This feature is discussed under "I/O suspension", below. The normal
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	423 stdio destination manager will NOT cause this to happen.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	424 In any case, the return value is the same as the change in the value of
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	425 next_scanline.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	426
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	427
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	428 6. jpeg_finish_compress(...);
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	429
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	430 After all the image data has been written, call jpeg_finish_compress() to
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	431 complete the compression cycle. This step is ESSENTIAL to ensure that the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	432 last bufferload of data is written to the data destination.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	433 jpeg_finish_compress() also releases working memory associated with the JPEG
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	434 object.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	435
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	436 Typical code:
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	437
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	438 jpeg_finish_compress(&cinfo);
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	439
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	440 If using the stdio destination manager, don't forget to close the output
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	441 stdio stream (if necessary) afterwards.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	442
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	443 If you have requested a multi-pass operating mode, such as Huffman code
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	444 optimization, jpeg_finish_compress() will perform the additional passes using
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	445 data buffered by the first pass. In this case jpeg_finish_compress() may take
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	446 quite a while to complete. With the default compression parameters, this will
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	447 not happen.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	448
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	449 It is an error to call jpeg_finish_compress() before writing the necessary
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	450 total number of scanlines. If you wish to abort compression, call
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	451 jpeg_abort() as discussed below.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	452
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	453 After completing a compression cycle, you may dispose of the JPEG object
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	454 as discussed next, or you may use it to compress another image. In that case
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	455 return to step 2, 3, or 4 as appropriate. If you do not change the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	456 destination manager, the new datastream will be written to the same target.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	457 If you do not change any JPEG parameters, the new datastream will be written
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	458 with the same parameters as before. Note that you can change the input image
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	459 dimensions freely between cycles, but if you change the input colorspace, you
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	460 should call jpeg_set_defaults() to adjust for the new colorspace; and then
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	461 you'll need to repeat all of step 3.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	462
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	463
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	464 7. Release the JPEG compression object.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	465
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	466 When you are done with a JPEG compression object, destroy it by calling
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	467 jpeg_destroy_compress(). This will free all subsidiary memory (regardless of
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	468 the previous state of the object). Or you can call jpeg_destroy(), which
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	469 works for either compression or decompression objects --- this may be more
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	470 convenient if you are sharing code between compression and decompression
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	471 cases. (Actually, these routines are equivalent except for the declared type
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	472 of the passed pointer. To avoid gripes from ANSI C compilers, jpeg_destroy()
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	473 should be passed a j_common_ptr.)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	474
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	475 If you allocated the jpeg_compress_struct structure from malloc(), freeing
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	476 it is your responsibility --- jpeg_destroy() won't. Ditto for the error
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	477 handler structure.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	478
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	479 Typical code:
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	480
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	481 jpeg_destroy_compress(&cinfo);
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	482
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	483
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	484 8. Aborting.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	485
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	486 If you decide to abort a compression cycle before finishing, you can clean up
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	487 in either of two ways:
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	488
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	489 * If you don't need the JPEG object any more, just call
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	490 jpeg_destroy_compress() or jpeg_destroy() to release memory. This is
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	491 legitimate at any point after calling jpeg_create_compress() --- in fact,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	492 it's safe even if jpeg_create_compress() fails.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	493
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	494 * If you want to re-use the JPEG object, call jpeg_abort_compress(), or call
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	495 jpeg_abort() which works on both compression and decompression objects.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	496 This will return the object to an idle state, releasing any working memory.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	497 jpeg_abort() is allowed at any time after successful object creation.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	498
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	499 Note that cleaning up the data destination, if required, is your
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	500 responsibility; neither of these routines will call term_destination().
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	501 (See "Compressed data handling", below, for more about that.)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	502
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	503 jpeg_destroy() and jpeg_abort() are the only safe calls to make on a JPEG
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	504 object that has reported an error by calling error_exit (see "Error handling"
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	505 for more info). The internal state of such an object is likely to be out of
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	506 whack. Either of these two routines will return the object to a known state.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	507
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	508
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	509 Decompression details
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	510 ---------------------
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	511
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	512 Here we revisit the JPEG decompression outline given in the overview.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	513
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	514 1. Allocate and initialize a JPEG decompression object.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	515
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	516 This is just like initialization for compression, as discussed above,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	517 except that the object is a "struct jpeg_decompress_struct" and you
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	518 call jpeg_create_decompress(). Error handling is exactly the same.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	519
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	520 Typical code:
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	521
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	522 struct jpeg_decompress_struct cinfo;
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	523 struct jpeg_error_mgr jerr;
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	524 ...
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	525 cinfo.err = jpeg_std_error(&jerr);
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	526 jpeg_create_decompress(&cinfo);
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	527
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	528 (Both here and in the IJG code, we usually use variable name "cinfo" for
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	529 both compression and decompression objects.)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	530
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	531
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	532 2. Specify the source of the compressed data (eg, a file).
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	533
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	534 As previously mentioned, the JPEG library reads compressed data from a "data
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	535 source" module. The library includes one data source module which knows how
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	536 to read from memory or from a file (or any stdio stream). You can use your
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	537 own source module if you want to do something else, as discussed later.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	538
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	539 If you use the standard source module, you must open the source stdio stream
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	540 beforehand. Typical code for this step looks like:
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	541
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	542 FILE * infile;
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	543 ...
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	544 if ((infile = fopen(filename, "rb")) == NULL) {
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	545 fprintf(stderr, "can't open %s\n", filename);
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	546 exit(1);
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	547 }
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	548 jpeg_stdio_src(&cinfo, infile);
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	549
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	550 where the last line invokes the standard source module.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	551
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	552 WARNING: it is critical that the binary compressed data be read unchanged.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	553 On non-Unix systems the stdio library may perform newline translation or
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	554 otherwise corrupt binary data. To suppress this behavior, you may need to use
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	555 a "b" option to fopen (as shown above), or use setmode() or another routine to
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	556 put the stdio stream in binary mode. See cjpeg.c and djpeg.c for code that
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	557 has been found to work on many systems.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	558
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	559 You may not change the data source between calling jpeg_read_header() and
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	560 jpeg_finish_decompress(). If you wish to read a series of JPEG images from
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	561 a single source file, you should repeat the jpeg_read_header() to
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	562 jpeg_finish_decompress() sequence without reinitializing either the JPEG
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	563 object or the data source module; this prevents buffered input data from
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	564 being discarded.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	565
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	566
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	567 3. Call jpeg_read_header() to obtain image info.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	568
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	569 Typical code for this step is just
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	570
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	571 jpeg_read_header(&cinfo, TRUE);
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	572
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	573 This will read the source datastream header markers, up to the beginning
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	574 of the compressed data proper. On return, the image dimensions and other
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	575 info have been stored in the JPEG object. The application may wish to
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	576 consult this information before selecting decompression parameters.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	577
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	578 More complex code is necessary if
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	579 * A suspending data source is used --- in that case jpeg_read_header()
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	580 may return before it has read all the header data. See "I/O suspension",
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	581 below. The normal stdio source manager will NOT cause this to happen.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	582 * Abbreviated JPEG files are to be processed --- see the section on
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	583 abbreviated datastreams. Standard applications that deal only in
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	584 interchange JPEG files need not be concerned with this case either.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	585
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	586 It is permissible to stop at this point if you just wanted to find out the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	587 image dimensions and other header info for a JPEG file. In that case,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	588 call jpeg_destroy() when you are done with the JPEG object, or call
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	589 jpeg_abort() to return it to an idle state before selecting a new data
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	590 source and reading another header.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	591
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	592
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	593 4. Set parameters for decompression.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	594
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	595 jpeg_read_header() sets appropriate default decompression parameters based on
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	596 the properties of the image (in particular, its colorspace). However, you
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	597 may well want to alter these defaults before beginning the decompression.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	598 For example, the default is to produce full color output from a color file.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	599 If you want colormapped output you must ask for it. Other options allow the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	600 returned image to be scaled and allow various speed/quality tradeoffs to be
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	601 selected. "Decompression parameter selection", below, gives details.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	602
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	603 If the defaults are appropriate, nothing need be done at this step.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	604
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	605 Note that all default values are set by each call to jpeg_read_header().
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	606 If you reuse a decompression object, you cannot expect your parameter
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	607 settings to be preserved across cycles, as you can for compression.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	608 You must set desired parameter values each time.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	609
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	610
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	611 5. jpeg_start_decompress(...);
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	612
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	613 Once the parameter values are satisfactory, call jpeg_start_decompress() to
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	614 begin decompression. This will initialize internal state, allocate working
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	615 memory, and prepare for returning data.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	616
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	617 Typical code is just
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	618
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	619 jpeg_start_decompress(&cinfo);
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	620
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	621 If you have requested a multi-pass operating mode, such as 2-pass color
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	622 quantization, jpeg_start_decompress() will do everything needed before data
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	623 output can begin. In this case jpeg_start_decompress() may take quite a while
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	624 to complete. With a single-scan (non progressive) JPEG file and default
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	625 decompression parameters, this will not happen; jpeg_start_decompress() will
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	626 return quickly.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	627
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	628 After this call, the final output image dimensions, including any requested
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	629 scaling, are available in the JPEG object; so is the selected colormap, if
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	630 colormapped output has been requested. Useful fields include
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	631
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	632 output_width image width and height, as scaled
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	633 output_height
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	634 out_color_components # of color components in out_color_space
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	635 output_components # of color components returned per pixel
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	636 colormap the selected colormap, if any
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	637 actual_number_of_colors number of entries in colormap
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	638
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	639 output_components is 1 (a colormap index) when quantizing colors; otherwise it
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	640 equals out_color_components. It is the number of JSAMPLE values that will be
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	641 emitted per pixel in the output arrays.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	642
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	643 Typically you will need to allocate data buffers to hold the incoming image.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	644 You will need output_width * output_components JSAMPLEs per scanline in your
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	645 output buffer, and a total of output_height scanlines will be returned.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	646
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	647 Note: if you are using the JPEG library's internal memory manager to allocate
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	648 data buffers (as djpeg does), then the manager's protocol requires that you
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	649 request large buffers before calling jpeg_start_decompress(). This is a
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	650 little tricky since the output_XXX fields are not normally valid then. You
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	651 can make them valid by calling jpeg_calc_output_dimensions() after setting the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	652 relevant parameters (scaling, output color space, and quantization flag).
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	653
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	654
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	655 6. while (scan lines remain to be read)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	656 jpeg_read_scanlines(...);
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	657
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	658 Now you can read the decompressed image data by calling jpeg_read_scanlines()
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	659 one or more times. At each call, you pass in the maximum number of scanlines
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	660 to be read (ie, the height of your working buffer); jpeg_read_scanlines()
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	661 will return up to that many lines. The return value is the number of lines
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	662 actually read. The format of the returned data is discussed under "Data
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	663 formats", above. Don't forget that grayscale and color JPEGs will return
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	664 different data formats!
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	665
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	666 Image data is returned in top-to-bottom scanline order. If you must write
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	667 out the image in bottom-to-top order, you can use the JPEG library's virtual
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	668 array mechanism to invert the data efficiently. Examples of this can be
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	669 found in the sample application djpeg.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	670
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	671 The library maintains a count of the number of scanlines returned so far
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	672 in the output_scanline field of the JPEG object. Usually you can just use
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	673 this variable as the loop counter, so that the loop test looks like
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	674 "while (cinfo.output_scanline < cinfo.output_height)". (Note that the test
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	675 should NOT be against image_height, unless you never use scaling. The
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	676 image_height field is the height of the original unscaled image.)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	677 The return value always equals the change in the value of output_scanline.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	678
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	679 If you don't use a suspending data source, it is safe to assume that
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	680 jpeg_read_scanlines() reads at least one scanline per call, until the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	681 bottom of the image has been reached.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	682
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	683 If you use a buffer larger than one scanline, it is NOT safe to assume that
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	684 jpeg_read_scanlines() fills it. (The current implementation returns only a
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	685 few scanlines per call, no matter how large a buffer you pass.) So you must
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	686 always provide a loop that calls jpeg_read_scanlines() repeatedly until the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	687 whole image has been read.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	688
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	689
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	690 7. jpeg_finish_decompress(...);
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	691
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	692 After all the image data has been read, call jpeg_finish_decompress() to
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	693 complete the decompression cycle. This causes working memory associated
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	694 with the JPEG object to be released.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	695
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	696 Typical code:
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	697
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	698 jpeg_finish_decompress(&cinfo);
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	699
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	700 If using the stdio source manager, don't forget to close the source stdio
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	701 stream if necessary.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	702
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	703 It is an error to call jpeg_finish_decompress() before reading the correct
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	704 total number of scanlines. If you wish to abort decompression, call
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	705 jpeg_abort() as discussed below.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	706
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	707 After completing a decompression cycle, you may dispose of the JPEG object as
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	708 discussed next, or you may use it to decompress another image. In that case
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	709 return to step 2 or 3 as appropriate. If you do not change the source
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	710 manager, the next image will be read from the same source.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	711
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	712
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	713 8. Release the JPEG decompression object.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	714
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	715 When you are done with a JPEG decompression object, destroy it by calling
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	716 jpeg_destroy_decompress() or jpeg_destroy(). The previous discussion of
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	717 destroying compression objects applies here too.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	718
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	719 Typical code:
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	720
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	721 jpeg_destroy_decompress(&cinfo);
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	722
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	723
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	724 9. Aborting.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	725
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	726 You can abort a decompression cycle by calling jpeg_destroy_decompress() or
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	727 jpeg_destroy() if you don't need the JPEG object any more, or
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	728 jpeg_abort_decompress() or jpeg_abort() if you want to reuse the object.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	729 The previous discussion of aborting compression cycles applies here too.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	730
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	731
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	732 Mechanics of usage: include files, linking, etc
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	733 -----------------------------------------------
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	734
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	735 Applications using the JPEG library should include the header file jpeglib.h
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	736 to obtain declarations of data types and routines. Before including
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	737 jpeglib.h, include system headers that define at least the typedefs FILE and
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	738 size_t. On ANSI-conforming systems, including <stdio.h> is sufficient; on
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	739 older Unix systems, you may need <sys/types.h> to define size_t.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	740
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	741 If the application needs to refer to individual JPEG library error codes, also
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	742 include jerror.h to define those symbols.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	743
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	744 jpeglib.h indirectly includes the files jconfig.h and jmorecfg.h. If you are
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	745 installing the JPEG header files in a system directory, you will want to
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	746 install all four files: jpeglib.h, jerror.h, jconfig.h, jmorecfg.h.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	747
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	748 The most convenient way to include the JPEG code into your executable program
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	749 is to prepare a library file ("libjpeg.a", or a corresponding name on non-Unix
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	750 machines) and reference it at your link step. If you use only half of the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	751 library (only compression or only decompression), only that much code will be
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	752 included from the library, unless your linker is hopelessly brain-damaged.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	753 The supplied makefiles build libjpeg.a automatically (see install.txt).
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	754
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	755 While you can build the JPEG library as a shared library if the whim strikes
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	756 you, we don't really recommend it. The trouble with shared libraries is that
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	757 at some point you'll probably try to substitute a new version of the library
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	758 without recompiling the calling applications. That generally doesn't work
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	759 because the parameter struct declarations usually change with each new
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	760 version. In other words, the library's API is not guaranteed binary
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	761 compatible across versions; we only try to ensure source-code compatibility.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	762 (In hindsight, it might have been smarter to hide the parameter structs from
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	763 applications and introduce a ton of access functions instead. Too late now,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	764 however.)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	765
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	766 On some systems your application may need to set up a signal handler to ensure
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	767 that temporary files are deleted if the program is interrupted. This is most
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	768 critical if you are on MS-DOS and use the jmemdos.c memory manager back end;
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	769 it will try to grab extended memory for temp files, and that space will NOT be
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	770 freed automatically. See cjpeg.c or djpeg.c for an example signal handler.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	771
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	772 It may be worth pointing out that the core JPEG library does not actually
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	773 require the stdio library: only the default source/destination managers and
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	774 error handler need it. You can use the library in a stdio-less environment
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	775 if you replace those modules and use jmemnobs.c (or another memory manager of
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	776 your own devising). More info about the minimum system library requirements
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	777 may be found in jinclude.h.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	778
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	779
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	780 ADVANCED FEATURES
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	781 =================
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	782
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	783 Compression parameter selection
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	784 -------------------------------
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	785
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	786 This section describes all the optional parameters you can set for JPEG
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	787 compression, as well as the "helper" routines provided to assist in this
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	788 task. Proper setting of some parameters requires detailed understanding
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	789 of the JPEG standard; if you don't know what a parameter is for, it's best
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	790 not to mess with it! See REFERENCES in the README file for pointers to
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	791 more info about JPEG.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	792
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	793 It's a good idea to call jpeg_set_defaults() first, even if you plan to set
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	794 all the parameters; that way your code is more likely to work with future JPEG
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	795 libraries that have additional parameters. For the same reason, we recommend
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	796 you use a helper routine where one is provided, in preference to twiddling
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	797 cinfo fields directly.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	798
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	799 The helper routines are:
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	800
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	801 jpeg_set_defaults (j_compress_ptr cinfo)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	802 This routine sets all JPEG parameters to reasonable defaults, using
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	803 only the input image's color space (field in_color_space, which must
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	804 already be set in cinfo). Many applications will only need to use
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	805 this routine and perhaps jpeg_set_quality().
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	806
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	807 jpeg_set_colorspace (j_compress_ptr cinfo, J_COLOR_SPACE colorspace)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	808 Sets the JPEG file's colorspace (field jpeg_color_space) as specified,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	809 and sets other color-space-dependent parameters appropriately. See
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	810 "Special color spaces", below, before using this. A large number of
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	811 parameters, including all per-component parameters, are set by this
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	812 routine; if you want to twiddle individual parameters you should call
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	813 jpeg_set_colorspace() before rather than after.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	814
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	815 jpeg_default_colorspace (j_compress_ptr cinfo)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	816 Selects an appropriate JPEG colorspace based on cinfo->in_color_space,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	817 and calls jpeg_set_colorspace(). This is actually a subroutine of
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	818 jpeg_set_defaults(). It's broken out in case you want to change
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	819 just the colorspace-dependent JPEG parameters.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	820
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	821 jpeg_set_quality (j_compress_ptr cinfo, int quality, boolean force_baseline)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	822 Constructs JPEG quantization tables appropriate for the indicated
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	823 quality setting. The quality value is expressed on the 0..100 scale
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	824 recommended by IJG (cjpeg's "-quality" switch uses this routine).
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	825 Note that the exact mapping from quality values to tables may change
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	826 in future IJG releases as more is learned about DCT quantization.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	827 If the force_baseline parameter is TRUE, then the quantization table
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	828 entries are constrained to the range 1..255 for full JPEG baseline
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	829 compatibility. In the current implementation, this only makes a
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	830 difference for quality settings below 25, and it effectively prevents
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	831 very small/low quality files from being generated. The IJG decoder
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	832 is capable of reading the non-baseline files generated at low quality
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	833 settings when force_baseline is FALSE, but other decoders may not be.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	834
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	835 jpeg_set_linear_quality (j_compress_ptr cinfo, int scale_factor,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	836 boolean force_baseline)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	837 Same as jpeg_set_quality() except that the generated tables are the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	838 sample tables given in the JPEC spec section K.1, multiplied by the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	839 specified scale factor (which is expressed as a percentage; thus
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	840 scale_factor = 100 reproduces the spec's tables). Note that larger
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	841 scale factors give lower quality. This entry point is useful for
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	842 conforming to the Adobe PostScript DCT conventions, but we do not
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	843 recommend linear scaling as a user-visible quality scale otherwise.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	844 force_baseline again constrains the computed table entries to 1..255.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	845
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	846 int jpeg_quality_scaling (int quality)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	847 Converts a value on the IJG-recommended quality scale to a linear
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	848 scaling percentage. Note that this routine may change or go away
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	849 in future releases --- IJG may choose to adopt a scaling method that
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	850 can't be expressed as a simple scalar multiplier, in which case the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	851 premise of this routine collapses. Caveat user.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	852
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	853 jpeg_default_qtables (j_compress_ptr cinfo, boolean force_baseline)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	854 Set default quantization tables with linear q_scale_factor[] values
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	855 (see below).
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	856
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	857 jpeg_add_quant_table (j_compress_ptr cinfo, int which_tbl,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	858 const unsigned int *basic_table,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	859 int scale_factor, boolean force_baseline)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	860 Allows an arbitrary quantization table to be created. which_tbl
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	861 indicates which table slot to fill. basic_table points to an array
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	862 of 64 unsigned ints given in normal array order. These values are
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	863 multiplied by scale_factor/100 and then clamped to the range 1..65535
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	864 (or to 1..255 if force_baseline is TRUE).
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	865 CAUTION: prior to library version 6a, jpeg_add_quant_table expected
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	866 the basic table to be given in JPEG zigzag order. If you need to
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	867 write code that works with either older or newer versions of this
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	868 routine, you must check the library version number. Something like
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	869 "#if JPEG_LIB_VERSION >= 61" is the right test.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	870
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	871 jpeg_simple_progression (j_compress_ptr cinfo)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	872 Generates a default scan script for writing a progressive-JPEG file.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	873 This is the recommended method of creating a progressive file,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	874 unless you want to make a custom scan sequence. You must ensure that
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	875 the JPEG color space is set correctly before calling this routine.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	876
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	877
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	878 Compression parameters (cinfo fields) include:
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	879
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	880 boolean arith_code
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	881 If TRUE, use arithmetic coding.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	882 If FALSE, use Huffman coding.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	883
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	884 int block_size
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	885 Set DCT block size. All N from 1 to 16 are possible.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	886 Default is 8 (baseline format).
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	887 Larger values produce higher compression,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	888 smaller values produce higher quality.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	889 An exact DCT stage is possible with 1 or 2.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	890 With the default quality of 75 and default quantization tables
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	891 the DCT+Quantization stage is lossless for value 1.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	892 Note that values other than 8 require a SmartScale capable decoder,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	893 introduced with IJG JPEG 8. Setting the block_size parameter for
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	894 compression works with version 8c and later.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	895
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	896 J_DCT_METHOD dct_method
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	897 Selects the algorithm used for the DCT step. Choices are:
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	898 JDCT_ISLOW: slow but accurate integer algorithm
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	899 JDCT_IFAST: faster, less accurate integer method
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	900 JDCT_FLOAT: floating-point method
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	901 JDCT_DEFAULT: default method (normally JDCT_ISLOW)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	902 JDCT_FASTEST: fastest method (normally JDCT_IFAST)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	903 The FLOAT method is very slightly more accurate than the ISLOW method,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	904 but may give different results on different machines due to varying
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	905 roundoff behavior. The integer methods should give the same results
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	906 on all machines. On machines with sufficiently fast FP hardware, the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	907 floating-point method may also be the fastest. The IFAST method is
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	908 considerably less accurate than the other two; its use is not
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	909 recommended if high quality is a concern. JDCT_DEFAULT and
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	910 JDCT_FASTEST are macros configurable by each installation.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	911
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	912 unsigned int scale_num, scale_denom
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	913 Scale the image by the fraction scale_num/scale_denom. Default is
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	914 1/1, or no scaling. Currently, the supported scaling ratios are
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	915 M/N with all N from 1 to 16, where M is the destination DCT size,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	916 which is 8 by default (see block_size parameter above).
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	917 (The library design allows for arbitrary scaling ratios but this
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	918 is not likely to be implemented any time soon.)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	919
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	920 J_COLOR_SPACE jpeg_color_space
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	921 int num_components
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	922 The JPEG color space and corresponding number of components; see
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	923 "Special color spaces", below, for more info. We recommend using
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	924 jpeg_set_colorspace() if you want to change these.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	925
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	926 J_COLOR_TRANSFORM color_transform
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	927 Internal color transform identifier, writes LSE marker if nonzero
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	928 (requires decoder with inverse color transform support, introduced
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	929 with IJG JPEG 9).
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	930 Two values are currently possible: JCT_NONE and JCT_SUBTRACT_GREEN.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	931 Set this value for lossless RGB application before calling
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	932 jpeg_set_colorspace(), because entropy table assignment in
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	933 jpeg_set_colorspace() depends on color_transform.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	934
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	935 boolean optimize_coding
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	936 TRUE causes the compressor to compute optimal Huffman coding tables
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	937 for the image. This requires an extra pass over the data and
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	938 therefore costs a good deal of space and time. The default is
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	939 FALSE, which tells the compressor to use the supplied or default
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	940 Huffman tables. In most cases optimal tables save only a few percent
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	941 of file size compared to the default tables. Note that when this is
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	942 TRUE, you need not supply Huffman tables at all, and any you do
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	943 supply will be overwritten.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	944
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	945 unsigned int restart_interval
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	946 int restart_in_rows
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	947 To emit restart markers in the JPEG file, set one of these nonzero.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	948 Set restart_interval to specify the exact interval in MCU blocks.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	949 Set restart_in_rows to specify the interval in MCU rows. (If
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	950 restart_in_rows is not 0, then restart_interval is set after the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	951 image width in MCUs is computed.) Defaults are zero (no restarts).
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	952 One restart marker per MCU row is often a good choice.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	953 NOTE: the overhead of restart markers is higher in grayscale JPEG
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	954 files than in color files, and MUCH higher in progressive JPEGs.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	955 If you use restarts, you may want to use larger intervals in those
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	956 cases.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	957
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	958 const jpeg_scan_info * scan_info
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	959 int num_scans
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	960 By default, scan_info is NULL; this causes the compressor to write a
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	961 single-scan sequential JPEG file. If not NULL, scan_info points to
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	962 an array of scan definition records of length num_scans. The
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	963 compressor will then write a JPEG file having one scan for each scan
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	964 definition record. This is used to generate noninterleaved or
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	965 progressive JPEG files. The library checks that the scan array
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	966 defines a valid JPEG scan sequence. (jpeg_simple_progression creates
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	967 a suitable scan definition array for progressive JPEG.) This is
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	968 discussed further under "Progressive JPEG support".
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	969
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	970 boolean do_fancy_downsampling
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	971 If TRUE, use direct DCT scaling with DCT size > 8 for downsampling
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	972 of chroma components.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	973 If FALSE, use only DCT size <= 8 and simple separate downsampling.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	974 Default is TRUE.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	975 For better image stability in multiple generation compression cycles
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	976 it is preferable that this value matches the corresponding
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	977 do_fancy_upsampling value in decompression.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	978
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	979 int smoothing_factor
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	980 If non-zero, the input image is smoothed; the value should be 1 for
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	981 minimal smoothing to 100 for maximum smoothing. Consult jcsample.c
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	982 for details of the smoothing algorithm. The default is zero.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	983
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	984 boolean write_JFIF_header
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	985 If TRUE, a JFIF APP0 marker is emitted. jpeg_set_defaults() and
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	986 jpeg_set_colorspace() set this TRUE if a JFIF-legal JPEG color space
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	987 (ie, YCbCr or grayscale) is selected, otherwise FALSE.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	988
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	989 UINT8 JFIF_major_version
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	990 UINT8 JFIF_minor_version
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	991 The version number to be written into the JFIF marker.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	992 jpeg_set_defaults() initializes the version to 1.01 (major=minor=1).
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	993 You should set it to 1.02 (major=1, minor=2) if you plan to write
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	994 any JFIF 1.02 extension markers.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	995
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	996 UINT8 density_unit
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	997 UINT16 X_density
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	998 UINT16 Y_density
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	999 The resolution information to be written into the JFIF marker;
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1000 not used otherwise. density_unit may be 0 for unknown,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1001 1 for dots/inch, or 2 for dots/cm. The default values are 0,1,1
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1002 indicating square pixels of unknown size.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1003
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1004 boolean write_Adobe_marker
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1005 If TRUE, an Adobe APP14 marker is emitted. jpeg_set_defaults() and
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1006 jpeg_set_colorspace() set this TRUE if JPEG color space RGB, CMYK,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1007 or YCCK is selected, otherwise FALSE. It is generally a bad idea
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1008 to set both write_JFIF_header and write_Adobe_marker. In fact,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1009 you probably shouldn't change the default settings at all --- the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1010 default behavior ensures that the JPEG file's color space can be
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1011 recognized by the decoder.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1012
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1013 JQUANT_TBL * quant_tbl_ptrs[NUM_QUANT_TBLS]
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1014 Pointers to coefficient quantization tables, one per table slot,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1015 or NULL if no table is defined for a slot. Usually these should
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1016 be set via one of the above helper routines; jpeg_add_quant_table()
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1017 is general enough to define any quantization table. The other
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1018 routines will set up table slot 0 for luminance quality and table
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1019 slot 1 for chrominance.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1020
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1021 int q_scale_factor[NUM_QUANT_TBLS]
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1022 Linear quantization scaling factors (percentage, initialized 100)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1023 for use with jpeg_default_qtables().
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1024 See rdswitch.c and cjpeg.c for an example of usage.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1025 Note that the q_scale_factor[] fields are the "linear" scales, so you
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1026 have to convert from user-defined ratings via jpeg_quality_scaling().
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1027 Here is an example code which corresponds to cjpeg -quality 90,70:
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1028
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1029 jpeg_set_defaults(cinfo);
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1030
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1031 /* Set luminance quality 90. */
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1032 cinfo->q_scale_factor[0] = jpeg_quality_scaling(90);
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1033 /* Set chrominance quality 70. */
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1034 cinfo->q_scale_factor[1] = jpeg_quality_scaling(70);
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1035
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1036 jpeg_default_qtables(cinfo, force_baseline);
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1037
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1038 CAUTION: You must also set 1x1 subsampling for efficient separate
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1039 color quality selection, since the default value used by library
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1040 is 2x2:
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1041
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1042 cinfo->comp_info[0].v_samp_factor = 1;
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1043 cinfo->comp_info[0].h_samp_factor = 1;
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1044
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1045 JHUFF_TBL * dc_huff_tbl_ptrs[NUM_HUFF_TBLS]
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1046 JHUFF_TBL * ac_huff_tbl_ptrs[NUM_HUFF_TBLS]
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1047 Pointers to Huffman coding tables, one per table slot, or NULL if
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1048 no table is defined for a slot. Slots 0 and 1 are filled with the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1049 JPEG sample tables by jpeg_set_defaults(). If you need to allocate
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1050 more table structures, jpeg_alloc_huff_table() may be used.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1051 Note that optimal Huffman tables can be computed for an image
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1052 by setting optimize_coding, as discussed above; there's seldom
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1053 any need to mess with providing your own Huffman tables.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1054
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1055
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1056 The actual dimensions of the JPEG image that will be written to the file are
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1057 given by the following fields. These are computed from the input image
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1058 dimensions and the compression parameters by jpeg_start_compress(). You can
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1059 also call jpeg_calc_jpeg_dimensions() to obtain the values that will result
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1060 from the current parameter settings. This can be useful if you are trying
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1061 to pick a scaling ratio that will get close to a desired target size.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1062
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1063 JDIMENSION jpeg_width Actual dimensions of output image.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1064 JDIMENSION jpeg_height
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1065
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1066
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1067 Per-component parameters are stored in the struct cinfo.comp_info[i] for
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1068 component number i. Note that components here refer to components of the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1069 JPEG color space, not the source image color space. A suitably large
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1070 comp_info[] array is allocated by jpeg_set_defaults(); if you choose not
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1071 to use that routine, it's up to you to allocate the array.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1072
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1073 int component_id
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1074 The one-byte identifier code to be recorded in the JPEG file for
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1075 this component. For the standard color spaces, we recommend you
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1076 leave the default values alone.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1077
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1078 int h_samp_factor
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1079 int v_samp_factor
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1080 Horizontal and vertical sampling factors for the component; must
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1081 be 1..4 according to the JPEG standard. Note that larger sampling
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1082 factors indicate a higher-resolution component; many people find
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1083 this behavior quite unintuitive. The default values are 2,2 for
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1084 luminance components and 1,1 for chrominance components, except
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1085 for grayscale where 1,1 is used.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1086
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1087 int quant_tbl_no
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1088 Quantization table number for component. The default value is
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1089 0 for luminance components and 1 for chrominance components.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1090
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1091 int dc_tbl_no
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1092 int ac_tbl_no
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1093 DC and AC entropy coding table numbers. The default values are
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1094 0 for luminance components and 1 for chrominance components.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1095
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1096 int component_index
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1097 Must equal the component's index in comp_info[]. (Beginning in
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1098 release v6, the compressor library will fill this in automatically;
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1099 you don't have to.)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1100
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1101
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1102 Decompression parameter selection
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1103 ---------------------------------
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1104
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1105 Decompression parameter selection is somewhat simpler than compression
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1106 parameter selection, since all of the JPEG internal parameters are
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1107 recorded in the source file and need not be supplied by the application.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1108 (Unless you are working with abbreviated files, in which case see
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1109 "Abbreviated datastreams", below.) Decompression parameters control
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1110 the postprocessing done on the image to deliver it in a format suitable
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1111 for the application's use. Many of the parameters control speed/quality
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1112 tradeoffs, in which faster decompression may be obtained at the price of
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1113 a poorer-quality image. The defaults select the highest quality (slowest)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1114 processing.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1115
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1116 The following fields in the JPEG object are set by jpeg_read_header() and
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1117 may be useful to the application in choosing decompression parameters:
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1118
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1119 JDIMENSION image_width Width and height of image
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1120 JDIMENSION image_height
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1121 int num_components Number of color components
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1122 J_COLOR_SPACE jpeg_color_space Colorspace of image
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1123 boolean saw_JFIF_marker TRUE if a JFIF APP0 marker was seen
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1124 UINT8 JFIF_major_version Version information from JFIF marker
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1125 UINT8 JFIF_minor_version
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1126 UINT8 density_unit Resolution data from JFIF marker
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1127 UINT16 X_density
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1128 UINT16 Y_density
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1129 boolean saw_Adobe_marker TRUE if an Adobe APP14 marker was seen
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1130 UINT8 Adobe_transform Color transform code from Adobe marker
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1131
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1132 The JPEG color space, unfortunately, is something of a guess since the JPEG
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1133 standard proper does not provide a way to record it. In practice most files
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1134 adhere to the JFIF or Adobe conventions, and the decoder will recognize these
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1135 correctly. See "Special color spaces", below, for more info.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1136
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1137
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1138 The decompression parameters that determine the basic properties of the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1139 returned image are:
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1140
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1141 J_COLOR_SPACE out_color_space
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1142 Output color space. jpeg_read_header() sets an appropriate default
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1143 based on jpeg_color_space; typically it will be RGB or grayscale.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1144 The application can change this field to request output in a different
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1145 colorspace. For example, set it to JCS_GRAYSCALE to get grayscale
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1146 output from a color file. (This is useful for previewing: grayscale
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1147 output is faster than full color since the color components need not
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1148 be processed.) Note that not all possible color space transforms are
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1149 currently implemented; you may need to extend jdcolor.c if you want an
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1150 unusual conversion.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1151
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1152 unsigned int scale_num, scale_denom
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1153 Scale the image by the fraction scale_num/scale_denom. Currently,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1154 the supported scaling ratios are M/N with all M from 1 to 16, where
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1155 N is the source DCT size, which is 8 for baseline JPEG. (The library
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1156 design allows for arbitrary scaling ratios but this is not likely
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1157 to be implemented any time soon.) The values are initialized by
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1158 jpeg_read_header() with the source DCT size. For baseline JPEG
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1159 this is 8/8. If you change only the scale_num value while leaving
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1160 the other unchanged, then this specifies the DCT scaled size to be
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1161 applied on the given input. For baseline JPEG this is equivalent
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1162 to M/8 scaling, since the source DCT size for baseline JPEG is 8.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1163 Smaller scaling ratios permit significantly faster decoding since
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1164 fewer pixels need be processed and a simpler IDCT method can be used.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1165
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1166 boolean quantize_colors
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1167 If set TRUE, colormapped output will be delivered. Default is FALSE,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1168 meaning that full-color output will be delivered.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1169
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1170 The next three parameters are relevant only if quantize_colors is TRUE.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1171
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1172 int desired_number_of_colors
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1173 Maximum number of colors to use in generating a library-supplied color
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1174 map (the actual number of colors is returned in a different field).
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1175 Default 256. Ignored when the application supplies its own color map.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1176
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1177 boolean two_pass_quantize
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1178 If TRUE, an extra pass over the image is made to select a custom color
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1179 map for the image. This usually looks a lot better than the one-size-
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1180 fits-all colormap that is used otherwise. Default is TRUE. Ignored
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1181 when the application supplies its own color map.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1182
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1183 J_DITHER_MODE dither_mode
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1184 Selects color dithering method. Supported values are:
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1185 JDITHER_NONE no dithering: fast, very low quality
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1186 JDITHER_ORDERED ordered dither: moderate speed and quality
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1187 JDITHER_FS Floyd-Steinberg dither: slow, high quality
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1188 Default is JDITHER_FS. (At present, ordered dither is implemented
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1189 only in the single-pass, standard-colormap case. If you ask for
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1190 ordered dither when two_pass_quantize is TRUE or when you supply
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1191 an external color map, you'll get F-S dithering.)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1192
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1193 When quantize_colors is TRUE, the target color map is described by the next
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1194 two fields. colormap is set to NULL by jpeg_read_header(). The application
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1195 can supply a color map by setting colormap non-NULL and setting
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1196 actual_number_of_colors to the map size. Otherwise, jpeg_start_decompress()
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1197 selects a suitable color map and sets these two fields itself.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1198 [Implementation restriction: at present, an externally supplied colormap is
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1199 only accepted for 3-component output color spaces.]
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1200
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1201 JSAMPARRAY colormap
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1202 The color map, represented as a 2-D pixel array of out_color_components
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1203 rows and actual_number_of_colors columns. Ignored if not quantizing.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1204 CAUTION: if the JPEG library creates its own colormap, the storage
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1205 pointed to by this field is released by jpeg_finish_decompress().
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1206 Copy the colormap somewhere else first, if you want to save it.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1207
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1208 int actual_number_of_colors
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1209 The number of colors in the color map.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1210
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1211 Additional decompression parameters that the application may set include:
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1212
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1213 J_DCT_METHOD dct_method
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1214 Selects the algorithm used for the DCT step. Choices are the same
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1215 as described above for compression.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1216
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1217 boolean do_fancy_upsampling
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1218 If TRUE, use direct DCT scaling with DCT size > 8 for upsampling
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1219 of chroma components.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1220 If FALSE, use only DCT size <= 8 and simple separate upsampling.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1221 Default is TRUE.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1222 For better image stability in multiple generation compression cycles
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1223 it is preferable that this value matches the corresponding
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1224 do_fancy_downsampling value in compression.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1225
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1226 boolean do_block_smoothing
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1227 If TRUE, interblock smoothing is applied in early stages of decoding
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1228 progressive JPEG files; if FALSE, not. Default is TRUE. Early
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1229 progression stages look "fuzzy" with smoothing, "blocky" without.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1230 In any case, block smoothing ceases to be applied after the first few
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1231 AC coefficients are known to full accuracy, so it is relevant only
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1232 when using buffered-image mode for progressive images.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1233
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1234 boolean enable_1pass_quant
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1235 boolean enable_external_quant
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1236 boolean enable_2pass_quant
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1237 These are significant only in buffered-image mode, which is
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1238 described in its own section below.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1239
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1240
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1241 The output image dimensions are given by the following fields. These are
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1242 computed from the source image dimensions and the decompression parameters
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1243 by jpeg_start_decompress(). You can also call jpeg_calc_output_dimensions()
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1244 to obtain the values that will result from the current parameter settings.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1245 This can be useful if you are trying to pick a scaling ratio that will get
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1246 close to a desired target size. It's also important if you are using the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1247 JPEG library's memory manager to allocate output buffer space, because you
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1248 are supposed to request such buffers before jpeg_start_decompress().
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1249
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1250 JDIMENSION output_width Actual dimensions of output image.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1251 JDIMENSION output_height
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1252 int out_color_components Number of color components in out_color_space.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1253 int output_components Number of color components returned.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1254 int rec_outbuf_height Recommended height of scanline buffer.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1255
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1256 When quantizing colors, output_components is 1, indicating a single color map
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1257 index per pixel. Otherwise it equals out_color_components. The output arrays
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1258 are required to be output_width * output_components JSAMPLEs wide.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1259
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1260 rec_outbuf_height is the recommended minimum height (in scanlines) of the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1261 buffer passed to jpeg_read_scanlines(). If the buffer is smaller, the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1262 library will still work, but time will be wasted due to unnecessary data
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1263 copying. In high-quality modes, rec_outbuf_height is always 1, but some
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1264 faster, lower-quality modes set it to larger values (typically 2 to 4).
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1265 If you are going to ask for a high-speed processing mode, you may as well
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1266 go to the trouble of honoring rec_outbuf_height so as to avoid data copying.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1267 (An output buffer larger than rec_outbuf_height lines is OK, but won't
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1268 provide any material speed improvement over that height.)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1269
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1270
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1271 Special color spaces
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1272 --------------------
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1273
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1274 The JPEG standard itself is "color blind" and doesn't specify any particular
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1275 color space. It is customary to convert color data to a luminance/chrominance
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1276 color space before compressing, since this permits greater compression. The
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1277 existing JPEG file interchange format standards specify YCbCr or GRAYSCALE
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1278 data (JFIF version 1), GRAYSCALE, RGB, YCbCr, CMYK, or YCCK (Adobe), or BG_RGB
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1279 or BG_YCC (big gamut color spaces, JFIF version 2). For special applications
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1280 such as multispectral images, other color spaces can be used,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1281 but it must be understood that such files will be unportable.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1282
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1283 The JPEG library can handle the most common colorspace conversions (namely
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1284 RGB <=> YCbCr and CMYK <=> YCCK). It can also deal with data of an unknown
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1285 color space, passing it through without conversion. If you deal extensively
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1286 with an unusual color space, you can easily extend the library to understand
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1287 additional color spaces and perform appropriate conversions.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1288
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1289 For compression, the source data's color space is specified by field
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1290 in_color_space. This is transformed to the JPEG file's color space given
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1291 by jpeg_color_space. jpeg_set_defaults() chooses a reasonable JPEG color
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1292 space depending on in_color_space, but you can override this by calling
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1293 jpeg_set_colorspace(). Of course you must select a supported transformation.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1294 jccolor.c currently supports the following transformations:
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1295 RGB => YCbCr
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1296 RGB => GRAYSCALE
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1297 RGB => BG_YCC
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1298 YCbCr => GRAYSCALE
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1299 YCbCr => BG_YCC
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1300 CMYK => YCCK
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1301 plus the null transforms: GRAYSCALE => GRAYSCALE, RGB => RGB,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1302 BG_RGB => BG_RGB, YCbCr => YCbCr, BG_YCC => BG_YCC, CMYK => CMYK,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1303 YCCK => YCCK, and UNKNOWN => UNKNOWN.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1304
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1305 The file interchange format standards (JFIF and Adobe) specify APPn markers
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1306 that indicate the color space of the JPEG file. It is important to ensure
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1307 that these are written correctly, or omitted if the JPEG file's color space
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1308 is not one of the ones supported by the interchange standards.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1309 jpeg_set_colorspace() will set the compression parameters to include or omit
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1310 the APPn markers properly, so long as it is told the truth about the JPEG
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1311 color space. For example, if you are writing some random 3-component color
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1312 space without conversion, don't try to fake out the library by setting
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1313 in_color_space and jpeg_color_space to JCS_YCbCr; use JCS_UNKNOWN.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1314 You may want to write an APPn marker of your own devising to identify
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1315 the colorspace --- see "Special markers", below.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1316
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1317 When told that the color space is UNKNOWN, the library will default to using
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1318 luminance-quality compression parameters for all color components. You may
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1319 well want to change these parameters. See the source code for
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1320 jpeg_set_colorspace(), in jcparam.c, for details.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1321
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1322 For decompression, the JPEG file's color space is given in jpeg_color_space,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1323 and this is transformed to the output color space out_color_space.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1324 jpeg_read_header's setting of jpeg_color_space can be relied on if the file
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1325 conforms to JFIF or Adobe conventions, but otherwise it is no better than a
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1326 guess. If you know the JPEG file's color space for certain, you can override
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1327 jpeg_read_header's guess by setting jpeg_color_space. jpeg_read_header also
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1328 selects a default output color space based on (its guess of) jpeg_color_space;
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1329 set out_color_space to override this. Again, you must select a supported
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1330 transformation. jdcolor.c currently supports
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1331 YCbCr => RGB
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1332 YCbCr => GRAYSCALE
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1333 BG_YCC => RGB
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1334 BG_YCC => GRAYSCALE
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1335 RGB => GRAYSCALE
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1336 GRAYSCALE => RGB
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1337 YCCK => CMYK
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1338 as well as the null transforms. (Since GRAYSCALE=>RGB is provided, an
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1339 application can force grayscale JPEGs to look like color JPEGs if it only
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1340 wants to handle one case.)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1341
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1342 The two-pass color quantizer, jquant2.c, is specialized to handle RGB data
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1343 (it weights distances appropriately for RGB colors). You'll need to modify
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1344 the code if you want to use it for non-RGB output color spaces. Note that
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1345 jquant2.c is used to map to an application-supplied colormap as well as for
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1346 the normal two-pass colormap selection process.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1347
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1348 CAUTION: it appears that Adobe Photoshop writes inverted data in CMYK JPEG
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1349 files: 0 represents 100% ink coverage, rather than 0% ink as you'd expect.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1350 This is arguably a bug in Photoshop, but if you need to work with Photoshop
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1351 CMYK files, you will have to deal with it in your application. We cannot
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1352 "fix" this in the library by inverting the data during the CMYK<=>YCCK
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1353 transform, because that would break other applications, notably Ghostscript.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1354 Photoshop versions prior to 3.0 write EPS files containing JPEG-encoded CMYK
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1355 data in the same inverted-YCCK representation used in bare JPEG files, but
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1356 the surrounding PostScript code performs an inversion using the PS image
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1357 operator. I am told that Photoshop 3.0 will write uninverted YCCK in
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1358 EPS/JPEG files, and will omit the PS-level inversion. (But the data
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1359 polarity used in bare JPEG files will not change in 3.0.) In either case,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1360 the JPEG library must not invert the data itself, or else Ghostscript would
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1361 read these EPS files incorrectly.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1362
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1363
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1364 Error handling
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1365 --------------
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1366
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1367 When the default error handler is used, any error detected inside the JPEG
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1368 routines will cause a message to be printed on stderr, followed by exit().
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1369 You can supply your own error handling routines to override this behavior
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1370 and to control the treatment of nonfatal warnings and trace/debug messages.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1371 The file example.c illustrates the most common case, which is to have the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1372 application regain control after an error rather than exiting.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1373
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1374 The JPEG library never writes any message directly; it always goes through
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1375 the error handling routines. Three classes of messages are recognized:
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1376 * Fatal errors: the library cannot continue.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1377 * Warnings: the library can continue, but the data is corrupt, and a
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1378 damaged output image is likely to result.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1379 * Trace/informational messages. These come with a trace level indicating
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1380 the importance of the message; you can control the verbosity of the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1381 program by adjusting the maximum trace level that will be displayed.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1382
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1383 You may, if you wish, simply replace the entire JPEG error handling module
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1384 (jerror.c) with your own code. However, you can avoid code duplication by
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1385 only replacing some of the routines depending on the behavior you need.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1386 This is accomplished by calling jpeg_std_error() as usual, but then overriding
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1387 some of the method pointers in the jpeg_error_mgr struct, as illustrated by
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1388 example.c.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1389
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1390 All of the error handling routines will receive a pointer to the JPEG object
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1391 (a j_common_ptr which points to either a jpeg_compress_struct or a
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1392 jpeg_decompress_struct; if you need to tell which, test the is_decompressor
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1393 field). This struct includes a pointer to the error manager struct in its
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1394 "err" field. Frequently, custom error handler routines will need to access
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1395 additional data which is not known to the JPEG library or the standard error
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1396 handler. The most convenient way to do this is to embed either the JPEG
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1397 object or the jpeg_error_mgr struct in a larger structure that contains
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1398 additional fields; then casting the passed pointer provides access to the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1399 additional fields. Again, see example.c for one way to do it. (Beginning
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1400 with IJG version 6b, there is also a void pointer "client_data" in each
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1401 JPEG object, which the application can also use to find related data.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1402 The library does not touch client_data at all.)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1403
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1404 The individual methods that you might wish to override are:
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1405
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1406 error_exit (j_common_ptr cinfo)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1407 Receives control for a fatal error. Information sufficient to
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1408 generate the error message has been stored in cinfo->err; call
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1409 output_message to display it. Control must NOT return to the caller;
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1410 generally this routine will exit() or longjmp() somewhere.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1411 Typically you would override this routine to get rid of the exit()
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1412 default behavior. Note that if you continue processing, you should
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1413 clean up the JPEG object with jpeg_abort() or jpeg_destroy().
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1414
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1415 output_message (j_common_ptr cinfo)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1416 Actual output of any JPEG message. Override this to send messages
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1417 somewhere other than stderr. Note that this method does not know
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1418 how to generate a message, only where to send it.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1419
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1420 format_message (j_common_ptr cinfo, char * buffer)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1421 Constructs a readable error message string based on the error info
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1422 stored in cinfo->err. This method is called by output_message. Few
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1423 applications should need to override this method. One possible
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1424 reason for doing so is to implement dynamic switching of error message
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1425 language.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1426
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1427 emit_message (j_common_ptr cinfo, int msg_level)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1428 Decide whether or not to emit a warning or trace message; if so,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1429 calls output_message. The main reason for overriding this method
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1430 would be to abort on warnings. msg_level is -1 for warnings,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1431 0 and up for trace messages.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1432
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1433 Only error_exit() and emit_message() are called from the rest of the JPEG
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1434 library; the other two are internal to the error handler.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1435
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1436 The actual message texts are stored in an array of strings which is pointed to
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1437 by the field err->jpeg_message_table. The messages are numbered from 0 to
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1438 err->last_jpeg_message, and it is these code numbers that are used in the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1439 JPEG library code. You could replace the message texts (for instance, with
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1440 messages in French or German) by changing the message table pointer. See
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1441 jerror.h for the default texts. CAUTION: this table will almost certainly
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1442 change or grow from one library version to the next.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1443
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1444 It may be useful for an application to add its own message texts that are
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1445 handled by the same mechanism. The error handler supports a second "add-on"
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1446 message table for this purpose. To define an addon table, set the pointer
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1447 err->addon_message_table and the message numbers err->first_addon_message and
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1448 err->last_addon_message. If you number the addon messages beginning at 1000
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1449 or so, you won't have to worry about conflicts with the library's built-in
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1450 messages. See the sample applications cjpeg/djpeg for an example of using
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1451 addon messages (the addon messages are defined in cderror.h).
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1452
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1453 Actual invocation of the error handler is done via macros defined in jerror.h:
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1454 ERREXITn(...) for fatal errors
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1455 WARNMSn(...) for corrupt-data warnings
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1456 TRACEMSn(...) for trace and informational messages.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1457 These macros store the message code and any additional parameters into the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1458 error handler struct, then invoke the error_exit() or emit_message() method.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1459 The variants of each macro are for varying numbers of additional parameters.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1460 The additional parameters are inserted into the generated message using
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1461 standard printf() format codes.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1462
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1463 See jerror.h and jerror.c for further details.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1464
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1465
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1466 Compressed data handling (source and destination managers)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1467 ----------------------------------------------------------
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1468
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1469 The JPEG compression library sends its compressed data to a "destination
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1470 manager" module. The default destination manager just writes the data to a
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1471 memory buffer or to a stdio stream, but you can provide your own manager to
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1472 do something else. Similarly, the decompression library calls a "source
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1473 manager" to obtain the compressed data; you can provide your own source
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1474 manager if you want the data to come from somewhere other than a memory
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1475 buffer or a stdio stream.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1476
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1477 In both cases, compressed data is processed a bufferload at a time: the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1478 destination or source manager provides a work buffer, and the library invokes
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1479 the manager only when the buffer is filled or emptied. (You could define a
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1480 one-character buffer to force the manager to be invoked for each byte, but
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1481 that would be rather inefficient.) The buffer's size and location are
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1482 controlled by the manager, not by the library. For example, the memory
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1483 source manager just makes the buffer pointer and length point to the original
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1484 data in memory. In this case the buffer-reload procedure will be invoked
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1485 only if the decompressor ran off the end of the datastream, which would
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1486 indicate an erroneous datastream.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1487
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1488 The work buffer is defined as an array of datatype JOCTET, which is generally
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1489 "char" or "unsigned char". On a machine where char is not exactly 8 bits
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1490 wide, you must define JOCTET as a wider data type and then modify the data
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1491 source and destination modules to transcribe the work arrays into 8-bit units
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1492 on external storage.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1493
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1494 A data destination manager struct contains a pointer and count defining the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1495 next byte to write in the work buffer and the remaining free space:
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1496
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1497 JOCTET * next_output_byte; /* => next byte to write in buffer */
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1498 size_t free_in_buffer; /* # of byte spaces remaining in buffer */
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1499
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1500 The library increments the pointer and decrements the count until the buffer
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1501 is filled. The manager's empty_output_buffer method must reset the pointer
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1502 and count. The manager is expected to remember the buffer's starting address
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1503 and total size in private fields not visible to the library.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1504
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1505 A data destination manager provides three methods:
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1506
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1507 init_destination (j_compress_ptr cinfo)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1508 Initialize destination. This is called by jpeg_start_compress()
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1509 before any data is actually written. It must initialize
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1510 next_output_byte and free_in_buffer. free_in_buffer must be
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1511 initialized to a positive value.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1512
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1513 empty_output_buffer (j_compress_ptr cinfo)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1514 This is called whenever the buffer has filled (free_in_buffer
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1515 reaches zero). In typical applications, it should write out the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1516 entire buffer (use the saved start address and buffer length;
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1517 ignore the current state of next_output_byte and free_in_buffer).
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1518 Then reset the pointer & count to the start of the buffer, and
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1519 return TRUE indicating that the buffer has been dumped.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1520 free_in_buffer must be set to a positive value when TRUE is
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1521 returned. A FALSE return should only be used when I/O suspension is
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1522 desired (this operating mode is discussed in the next section).
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1523
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1524 term_destination (j_compress_ptr cinfo)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1525 Terminate destination --- called by jpeg_finish_compress() after all
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1526 data has been written. In most applications, this must flush any
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1527 data remaining in the buffer. Use either next_output_byte or
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1528 free_in_buffer to determine how much data is in the buffer.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1529
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1530 term_destination() is NOT called by jpeg_abort() or jpeg_destroy(). If you
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1531 want the destination manager to be cleaned up during an abort, you must do it
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1532 yourself.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1533
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1534 You will also need code to create a jpeg_destination_mgr struct, fill in its
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1535 method pointers, and insert a pointer to the struct into the "dest" field of
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1536 the JPEG compression object. This can be done in-line in your setup code if
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1537 you like, but it's probably cleaner to provide a separate routine similar to
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1538 the jpeg_stdio_dest() or jpeg_mem_dest() routines of the supplied destination
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1539 managers.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1540
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1541 Decompression source managers follow a parallel design, but with some
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1542 additional frammishes. The source manager struct contains a pointer and count
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1543 defining the next byte to read from the work buffer and the number of bytes
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1544 remaining:
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1545
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1546 const JOCTET * next_input_byte; /* => next byte to read from buffer */
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1547 size_t bytes_in_buffer; /* # of bytes remaining in buffer */
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1548
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1549 The library increments the pointer and decrements the count until the buffer
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1550 is emptied. The manager's fill_input_buffer method must reset the pointer and
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1551 count. In most applications, the manager must remember the buffer's starting
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1552 address and total size in private fields not visible to the library.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1553
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1554 A data source manager provides five methods:
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1555
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1556 init_source (j_decompress_ptr cinfo)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1557 Initialize source. This is called by jpeg_read_header() before any
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1558 data is actually read. Unlike init_destination(), it may leave
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1559 bytes_in_buffer set to 0 (in which case a fill_input_buffer() call
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1560 will occur immediately).
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1561
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1562 fill_input_buffer (j_decompress_ptr cinfo)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1563 This is called whenever bytes_in_buffer has reached zero and more
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1564 data is wanted. In typical applications, it should read fresh data
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1565 into the buffer (ignoring the current state of next_input_byte and
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1566 bytes_in_buffer), reset the pointer & count to the start of the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1567 buffer, and return TRUE indicating that the buffer has been reloaded.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1568 It is not necessary to fill the buffer entirely, only to obtain at
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1569 least one more byte. bytes_in_buffer MUST be set to a positive value
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1570 if TRUE is returned. A FALSE return should only be used when I/O
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1571 suspension is desired (this mode is discussed in the next section).
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1572
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1573 skip_input_data (j_decompress_ptr cinfo, long num_bytes)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1574 Skip num_bytes worth of data. The buffer pointer and count should
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1575 be advanced over num_bytes input bytes, refilling the buffer as
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1576 needed. This is used to skip over a potentially large amount of
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1577 uninteresting data (such as an APPn marker). In some applications
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1578 it may be possible to optimize away the reading of the skipped data,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1579 but it's not clear that being smart is worth much trouble; large
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1580 skips are uncommon. bytes_in_buffer may be zero on return.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1581 A zero or negative skip count should be treated as a no-op.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1582
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1583 resync_to_restart (j_decompress_ptr cinfo, int desired)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1584 This routine is called only when the decompressor has failed to find
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1585 a restart (RSTn) marker where one is expected. Its mission is to
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1586 find a suitable point for resuming decompression. For most
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1587 applications, we recommend that you just use the default resync
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1588 procedure, jpeg_resync_to_restart(). However, if you are able to back
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1589 up in the input data stream, or if you have a-priori knowledge about
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1590 the likely location of restart markers, you may be able to do better.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1591 Read the read_restart_marker() and jpeg_resync_to_restart() routines
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1592 in jdmarker.c if you think you'd like to implement your own resync
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1593 procedure.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1594
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1595 term_source (j_decompress_ptr cinfo)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1596 Terminate source --- called by jpeg_finish_decompress() after all
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1597 data has been read. Often a no-op.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1598
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1599 For both fill_input_buffer() and skip_input_data(), there is no such thing
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1600 as an EOF return. If the end of the file has been reached, the routine has
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1601 a choice of exiting via ERREXIT() or inserting fake data into the buffer.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1602 In most cases, generating a warning message and inserting a fake EOI marker
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1603 is the best course of action --- this will allow the decompressor to output
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1604 however much of the image is there. In pathological cases, the decompressor
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1605 may swallow the EOI and again demand data ... just keep feeding it fake EOIs.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1606 jdatasrc.c illustrates the recommended error recovery behavior.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1607
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1608 term_source() is NOT called by jpeg_abort() or jpeg_destroy(). If you want
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1609 the source manager to be cleaned up during an abort, you must do it yourself.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1610
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1611 You will also need code to create a jpeg_source_mgr struct, fill in its method
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1612 pointers, and insert a pointer to the struct into the "src" field of the JPEG
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1613 decompression object. This can be done in-line in your setup code if you
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1614 like, but it's probably cleaner to provide a separate routine similar to the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1615 jpeg_stdio_src() or jpeg_mem_src() routines of the supplied source managers.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1616
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1617 For more information, consult the memory and stdio source and destination
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1618 managers in jdatasrc.c and jdatadst.c.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1619
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1620
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1621 I/O suspension
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1622 --------------
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1623
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1624 Some applications need to use the JPEG library as an incremental memory-to-
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1625 memory filter: when the compressed data buffer is filled or emptied, they want
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1626 control to return to the outer loop, rather than expecting that the buffer can
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1627 be emptied or reloaded within the data source/destination manager subroutine.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1628 The library supports this need by providing an "I/O suspension" mode, which we
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1629 describe in this section.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1630
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1631 The I/O suspension mode is not a panacea: nothing is guaranteed about the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1632 maximum amount of time spent in any one call to the library, so it will not
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1633 eliminate response-time problems in single-threaded applications. If you
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1634 need guaranteed response time, we suggest you "bite the bullet" and implement
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1635 a real multi-tasking capability.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1636
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1637 To use I/O suspension, cooperation is needed between the calling application
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1638 and the data source or destination manager; you will always need a custom
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1639 source/destination manager. (Please read the previous section if you haven't
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1640 already.) The basic idea is that the empty_output_buffer() or
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1641 fill_input_buffer() routine is a no-op, merely returning FALSE to indicate
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1642 that it has done nothing. Upon seeing this, the JPEG library suspends
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1643 operation and returns to its caller. The surrounding application is
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1644 responsible for emptying or refilling the work buffer before calling the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1645 JPEG library again.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1646
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1647 Compression suspension:
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1648
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1649 For compression suspension, use an empty_output_buffer() routine that returns
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1650 FALSE; typically it will not do anything else. This will cause the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1651 compressor to return to the caller of jpeg_write_scanlines(), with the return
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1652 value indicating that not all the supplied scanlines have been accepted.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1653 The application must make more room in the output buffer, adjust the output
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1654 buffer pointer/count appropriately, and then call jpeg_write_scanlines()
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1655 again, pointing to the first unconsumed scanline.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1656
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1657 When forced to suspend, the compressor will backtrack to a convenient stopping
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1658 point (usually the start of the current MCU); it will regenerate some output
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1659 data when restarted. Therefore, although empty_output_buffer() is only
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1660 called when the buffer is filled, you should NOT write out the entire buffer
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1661 after a suspension. Write only the data up to the current position of
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1662 next_output_byte/free_in_buffer. The data beyond that point will be
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1663 regenerated after resumption.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1664
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1665 Because of the backtracking behavior, a good-size output buffer is essential
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1666 for efficiency; you don't want the compressor to suspend often. (In fact, an
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1667 overly small buffer could lead to infinite looping, if a single MCU required
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1668 more data than would fit in the buffer.) We recommend a buffer of at least
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1669 several Kbytes. You may want to insert explicit code to ensure that you don't
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1670 call jpeg_write_scanlines() unless there is a reasonable amount of space in
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1671 the output buffer; in other words, flush the buffer before trying to compress
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1672 more data.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1673
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1674 The compressor does not allow suspension while it is trying to write JPEG
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1675 markers at the beginning and end of the file. This means that:
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1676 * At the beginning of a compression operation, there must be enough free
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1677 space in the output buffer to hold the header markers (typically 600 or
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1678 so bytes). The recommended buffer size is bigger than this anyway, so
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1679 this is not a problem as long as you start with an empty buffer. However,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1680 this restriction might catch you if you insert large special markers, such
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1681 as a JFIF thumbnail image, without flushing the buffer afterwards.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1682 * When you call jpeg_finish_compress(), there must be enough space in the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1683 output buffer to emit any buffered data and the final EOI marker. In the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1684 current implementation, half a dozen bytes should suffice for this, but
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1685 for safety's sake we recommend ensuring that at least 100 bytes are free
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1686 before calling jpeg_finish_compress().
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1687
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1688 A more significant restriction is that jpeg_finish_compress() cannot suspend.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1689 This means you cannot use suspension with multi-pass operating modes, namely
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1690 Huffman code optimization and multiple-scan output. Those modes write the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1691 whole file during jpeg_finish_compress(), which will certainly result in
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1692 buffer overrun. (Note that this restriction applies only to compression,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1693 not decompression. The decompressor supports input suspension in all of its
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1694 operating modes.)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1695
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1696 Decompression suspension:
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1697
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1698 For decompression suspension, use a fill_input_buffer() routine that simply
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1699 returns FALSE (except perhaps during error recovery, as discussed below).
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1700 This will cause the decompressor to return to its caller with an indication
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1701 that suspension has occurred. This can happen at four places:
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1702 * jpeg_read_header(): will return JPEG_SUSPENDED.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1703 * jpeg_start_decompress(): will return FALSE, rather than its usual TRUE.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1704 * jpeg_read_scanlines(): will return the number of scanlines already
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1705 completed (possibly 0).
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1706 * jpeg_finish_decompress(): will return FALSE, rather than its usual TRUE.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1707 The surrounding application must recognize these cases, load more data into
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1708 the input buffer, and repeat the call. In the case of jpeg_read_scanlines(),
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1709 increment the passed pointers past any scanlines successfully read.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1710
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1711 Just as with compression, the decompressor will typically backtrack to a
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1712 convenient restart point before suspending. When fill_input_buffer() is
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1713 called, next_input_byte/bytes_in_buffer point to the current restart point,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1714 which is where the decompressor will backtrack to if FALSE is returned.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1715 The data beyond that position must NOT be discarded if you suspend; it needs
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1716 to be re-read upon resumption. In most implementations, you'll need to shift
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1717 this data down to the start of your work buffer and then load more data after
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1718 it. Again, this behavior means that a several-Kbyte work buffer is essential
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1719 for decent performance; furthermore, you should load a reasonable amount of
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1720 new data before resuming decompression. (If you loaded, say, only one new
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1721 byte each time around, you could waste a LOT of cycles.)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1722
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1723 The skip_input_data() source manager routine requires special care in a
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1724 suspension scenario. This routine is NOT granted the ability to suspend the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1725 decompressor; it can decrement bytes_in_buffer to zero, but no more. If the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1726 requested skip distance exceeds the amount of data currently in the input
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1727 buffer, then skip_input_data() must set bytes_in_buffer to zero and record the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1728 additional skip distance somewhere else. The decompressor will immediately
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1729 call fill_input_buffer(), which should return FALSE, which will cause a
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1730 suspension return. The surrounding application must then arrange to discard
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1731 the recorded number of bytes before it resumes loading the input buffer.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1732 (Yes, this design is rather baroque, but it avoids complexity in the far more
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1733 common case where a non-suspending source manager is used.)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1734
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1735 If the input data has been exhausted, we recommend that you emit a warning
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1736 and insert dummy EOI markers just as a non-suspending data source manager
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1737 would do. This can be handled either in the surrounding application logic or
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1738 within fill_input_buffer(); the latter is probably more efficient. If
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1739 fill_input_buffer() knows that no more data is available, it can set the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1740 pointer/count to point to a dummy EOI marker and then return TRUE just as
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1741 though it had read more data in a non-suspending situation.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1742
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1743 The decompressor does not attempt to suspend within standard JPEG markers;
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1744 instead it will backtrack to the start of the marker and reprocess the whole
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1745 marker next time. Hence the input buffer must be large enough to hold the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1746 longest standard marker in the file. Standard JPEG markers should normally
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1747 not exceed a few hundred bytes each (DHT tables are typically the longest).
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1748 We recommend at least a 2K buffer for performance reasons, which is much
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1749 larger than any correct marker is likely to be. For robustness against
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1750 damaged marker length counts, you may wish to insert a test in your
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1751 application for the case that the input buffer is completely full and yet
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1752 the decoder has suspended without consuming any data --- otherwise, if this
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1753 situation did occur, it would lead to an endless loop. (The library can't
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1754 provide this test since it has no idea whether "the buffer is full", or
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1755 even whether there is a fixed-size input buffer.)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1756
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1757 The input buffer would need to be 64K to allow for arbitrary COM or APPn
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1758 markers, but these are handled specially: they are either saved into allocated
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1759 memory, or skipped over by calling skip_input_data(). In the former case,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1760 suspension is handled correctly, and in the latter case, the problem of
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1761 buffer overrun is placed on skip_input_data's shoulders, as explained above.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1762 Note that if you provide your own marker handling routine for large markers,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1763 you should consider how to deal with buffer overflow.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1764
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1765 Multiple-buffer management:
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1766
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1767 In some applications it is desirable to store the compressed data in a linked
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1768 list of buffer areas, so as to avoid data copying. This can be handled by
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1769 having empty_output_buffer() or fill_input_buffer() set the pointer and count
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1770 to reference the next available buffer; FALSE is returned only if no more
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1771 buffers are available. Although seemingly straightforward, there is a
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1772 pitfall in this approach: the backtrack that occurs when FALSE is returned
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1773 could back up into an earlier buffer. For example, when fill_input_buffer()
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1774 is called, the current pointer & count indicate the backtrack restart point.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1775 Since fill_input_buffer() will set the pointer and count to refer to a new
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1776 buffer, the restart position must be saved somewhere else. Suppose a second
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1777 call to fill_input_buffer() occurs in the same library call, and no
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1778 additional input data is available, so fill_input_buffer must return FALSE.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1779 If the JPEG library has not moved the pointer/count forward in the current
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1780 buffer, then *the correct restart point is the saved position in the prior
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1781 buffer*. Prior buffers may be discarded only after the library establishes
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1782 a restart point within a later buffer. Similar remarks apply for output into
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1783 a chain of buffers.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1784
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1785 The library will never attempt to backtrack over a skip_input_data() call,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1786 so any skipped data can be permanently discarded. You still have to deal
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1787 with the case of skipping not-yet-received data, however.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1788
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1789 It's much simpler to use only a single buffer; when fill_input_buffer() is
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1790 called, move any unconsumed data (beyond the current pointer/count) down to
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1791 the beginning of this buffer and then load new data into the remaining buffer
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1792 space. This approach requires a little more data copying but is far easier
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1793 to get right.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1794
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1795
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1796 Progressive JPEG support
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1797 ------------------------
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1798
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1799 Progressive JPEG rearranges the stored data into a series of scans of
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1800 increasing quality. In situations where a JPEG file is transmitted across a
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1801 slow communications link, a decoder can generate a low-quality image very
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1802 quickly from the first scan, then gradually improve the displayed quality as
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1803 more scans are received. The final image after all scans are complete is
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1804 identical to that of a regular (sequential) JPEG file of the same quality
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1805 setting. Progressive JPEG files are often slightly smaller than equivalent
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1806 sequential JPEG files, but the possibility of incremental display is the main
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1807 reason for using progressive JPEG.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1808
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1809 The IJG encoder library generates progressive JPEG files when given a
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1810 suitable "scan script" defining how to divide the data into scans.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1811 Creation of progressive JPEG files is otherwise transparent to the encoder.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1812 Progressive JPEG files can also be read transparently by the decoder library.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1813 If the decoding application simply uses the library as defined above, it
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1814 will receive a final decoded image without any indication that the file was
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1815 progressive. Of course, this approach does not allow incremental display.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1816 To perform incremental display, an application needs to use the decoder
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1817 library's "buffered-image" mode, in which it receives a decoded image
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1818 multiple times.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1819
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1820 Each displayed scan requires about as much work to decode as a full JPEG
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1821 image of the same size, so the decoder must be fairly fast in relation to the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1822 data transmission rate in order to make incremental display useful. However,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1823 it is possible to skip displaying the image and simply add the incoming bits
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1824 to the decoder's coefficient buffer. This is fast because only Huffman
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1825 decoding need be done, not IDCT, upsampling, colorspace conversion, etc.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1826 The IJG decoder library allows the application to switch dynamically between
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1827 displaying the image and simply absorbing the incoming bits. A properly
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1828 coded application can automatically adapt the number of display passes to
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1829 suit the time available as the image is received. Also, a final
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1830 higher-quality display cycle can be performed from the buffered data after
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1831 the end of the file is reached.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1832
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1833 Progressive compression:
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1834
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1835 To create a progressive JPEG file (or a multiple-scan sequential JPEG file),
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1836 set the scan_info cinfo field to point to an array of scan descriptors, and
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1837 perform compression as usual. Instead of constructing your own scan list,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1838 you can call the jpeg_simple_progression() helper routine to create a
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1839 recommended progression sequence; this method should be used by all
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1840 applications that don't want to get involved in the nitty-gritty of
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1841 progressive scan sequence design. (If you want to provide user control of
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1842 scan sequences, you may wish to borrow the scan script reading code found
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1843 in rdswitch.c, so that you can read scan script files just like cjpeg's.)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1844 When scan_info is not NULL, the compression library will store DCT'd data
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1845 into a buffer array as jpeg_write_scanlines() is called, and will emit all
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1846 the requested scans during jpeg_finish_compress(). This implies that
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1847 multiple-scan output cannot be created with a suspending data destination
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1848 manager, since jpeg_finish_compress() does not support suspension. We
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1849 should also note that the compressor currently forces Huffman optimization
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1850 mode when creating a progressive JPEG file, because the default Huffman
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1851 tables are unsuitable for progressive files.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1852
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1853 Progressive decompression:
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1854
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1855 When buffered-image mode is not used, the decoder library will read all of
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1856 a multi-scan file during jpeg_start_decompress(), so that it can provide a
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1857 final decoded image. (Here "multi-scan" means either progressive or
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1858 multi-scan sequential.) This makes multi-scan files transparent to the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1859 decoding application. However, existing applications that used suspending
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1860 input with version 5 of the IJG library will need to be modified to check
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1861 for a suspension return from jpeg_start_decompress().
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1862
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1863 To perform incremental display, an application must use the library's
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1864 buffered-image mode. This is described in the next section.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1865
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1866
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1867 Buffered-image mode
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1868 -------------------
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1869
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1870 In buffered-image mode, the library stores the partially decoded image in a
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1871 coefficient buffer, from which it can be read out as many times as desired.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1872 This mode is typically used for incremental display of progressive JPEG files,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1873 but it can be used with any JPEG file. Each scan of a progressive JPEG file
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1874 adds more data (more detail) to the buffered image. The application can
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1875 display in lockstep with the source file (one display pass per input scan),
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1876 or it can allow input processing to outrun display processing. By making
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1877 input and display processing run independently, it is possible for the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1878 application to adapt progressive display to a wide range of data transmission
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1879 rates.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1880
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1881 The basic control flow for buffered-image decoding is
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1882
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1883 jpeg_create_decompress()
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1884 set data source
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1885 jpeg_read_header()
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1886 set overall decompression parameters
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1887 cinfo.buffered_image = TRUE; /* select buffered-image mode */
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1888 jpeg_start_decompress()
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1889 for (each output pass) {
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1890 adjust output decompression parameters if required
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1891 jpeg_start_output() /* start a new output pass */
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1892 for (all scanlines in image) {
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1893 jpeg_read_scanlines()
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1894 display scanlines
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1895 }
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1896 jpeg_finish_output() /* terminate output pass */
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1897 }
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1898 jpeg_finish_decompress()
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1899 jpeg_destroy_decompress()
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1900
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1901 This differs from ordinary unbuffered decoding in that there is an additional
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1902 level of looping. The application can choose how many output passes to make
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1903 and how to display each pass.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1904
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1905 The simplest approach to displaying progressive images is to do one display
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1906 pass for each scan appearing in the input file. In this case the outer loop
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1907 condition is typically
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1908 while (! jpeg_input_complete(&cinfo))
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1909 and the start-output call should read
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1910 jpeg_start_output(&cinfo, cinfo.input_scan_number);
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1911 The second parameter to jpeg_start_output() indicates which scan of the input
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1912 file is to be displayed; the scans are numbered starting at 1 for this
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1913 purpose. (You can use a loop counter starting at 1 if you like, but using
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1914 the library's input scan counter is easier.) The library automatically reads
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1915 data as necessary to complete each requested scan, and jpeg_finish_output()
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1916 advances to the next scan or end-of-image marker (hence input_scan_number
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1917 will be incremented by the time control arrives back at jpeg_start_output()).
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1918 With this technique, data is read from the input file only as needed, and
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1919 input and output processing run in lockstep.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1920
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1921 After reading the final scan and reaching the end of the input file, the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1922 buffered image remains available; it can be read additional times by
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1923 repeating the jpeg_start_output()/jpeg_read_scanlines()/jpeg_finish_output()
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1924 sequence. For example, a useful technique is to use fast one-pass color
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1925 quantization for display passes made while the image is arriving, followed by
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1926 a final display pass using two-pass quantization for highest quality. This
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1927 is done by changing the library parameters before the final output pass.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1928 Changing parameters between passes is discussed in detail below.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1929
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1930 In general the last scan of a progressive file cannot be recognized as such
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1931 until after it is read, so a post-input display pass is the best approach if
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1932 you want special processing in the final pass.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1933
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1934 When done with the image, be sure to call jpeg_finish_decompress() to release
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1935 the buffered image (or just use jpeg_destroy_decompress()).
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1936
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1937 If input data arrives faster than it can be displayed, the application can
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1938 cause the library to decode input data in advance of what's needed to produce
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1939 output. This is done by calling the routine jpeg_consume_input().
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1940 The return value is one of the following:
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1941 JPEG_REACHED_SOS: reached an SOS marker (the start of a new scan)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1942 JPEG_REACHED_EOI: reached the EOI marker (end of image)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1943 JPEG_ROW_COMPLETED: completed reading one MCU row of compressed data
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1944 JPEG_SCAN_COMPLETED: completed reading last MCU row of current scan
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1945 JPEG_SUSPENDED: suspended before completing any of the above
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1946 (JPEG_SUSPENDED can occur only if a suspending data source is used.) This
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1947 routine can be called at any time after initializing the JPEG object. It
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1948 reads some additional data and returns when one of the indicated significant
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1949 events occurs. (If called after the EOI marker is reached, it will
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1950 immediately return JPEG_REACHED_EOI without attempting to read more data.)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1951
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1952 The library's output processing will automatically call jpeg_consume_input()
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1953 whenever the output processing overtakes the input; thus, simple lockstep
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1954 display requires no direct calls to jpeg_consume_input(). But by adding
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1955 calls to jpeg_consume_input(), you can absorb data in advance of what is
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1956 being displayed. This has two benefits:
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1957 * You can limit buildup of unprocessed data in your input buffer.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1958 * You can eliminate extra display passes by paying attention to the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1959 state of the library's input processing.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1960
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1961 The first of these benefits only requires interspersing calls to
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1962 jpeg_consume_input() with your display operations and any other processing
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1963 you may be doing. To avoid wasting cycles due to backtracking, it's best to
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1964 call jpeg_consume_input() only after a hundred or so new bytes have arrived.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1965 This is discussed further under "I/O suspension", above. (Note: the JPEG
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1966 library currently is not thread-safe. You must not call jpeg_consume_input()
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1967 from one thread of control if a different library routine is working on the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1968 same JPEG object in another thread.)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1969
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1970 When input arrives fast enough that more than one new scan is available
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1971 before you start a new output pass, you may as well skip the output pass
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1972 corresponding to the completed scan. This occurs for free if you pass
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1973 cinfo.input_scan_number as the target scan number to jpeg_start_output().
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1974 The input_scan_number field is simply the index of the scan currently being
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1975 consumed by the input processor. You can ensure that this is up-to-date by
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1976 emptying the input buffer just before calling jpeg_start_output(): call
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1977 jpeg_consume_input() repeatedly until it returns JPEG_SUSPENDED or
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1978 JPEG_REACHED_EOI.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1979
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1980 The target scan number passed to jpeg_start_output() is saved in the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1981 cinfo.output_scan_number field. The library's output processing calls
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1982 jpeg_consume_input() whenever the current input scan number and row within
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1983 that scan is less than or equal to the current output scan number and row.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1984 Thus, input processing can "get ahead" of the output processing but is not
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1985 allowed to "fall behind". You can achieve several different effects by
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1986 manipulating this interlock rule. For example, if you pass a target scan
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1987 number greater than the current input scan number, the output processor will
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1988 wait until that scan starts to arrive before producing any output. (To avoid
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1989 an infinite loop, the target scan number is automatically reset to the last
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1990 scan number when the end of image is reached. Thus, if you specify a large
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1991 target scan number, the library will just absorb the entire input file and
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1992 then perform an output pass. This is effectively the same as what
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1993 jpeg_start_decompress() does when you don't select buffered-image mode.)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1994 When you pass a target scan number equal to the current input scan number,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1995 the image is displayed no faster than the current input scan arrives. The
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1996 final possibility is to pass a target scan number less than the current input
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1997 scan number; this disables the input/output interlock and causes the output
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1998 processor to simply display whatever it finds in the image buffer, without
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	1999 waiting for input. (However, the library will not accept a target scan
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2000 number less than one, so you can't avoid waiting for the first scan.)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2001
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2002 When data is arriving faster than the output display processing can advance
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2003 through the image, jpeg_consume_input() will store data into the buffered
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2004 image beyond the point at which the output processing is reading data out
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2005 again. If the input arrives fast enough, it may "wrap around" the buffer to
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2006 the point where the input is more than one whole scan ahead of the output.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2007 If the output processing simply proceeds through its display pass without
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2008 paying attention to the input, the effect seen on-screen is that the lower
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2009 part of the image is one or more scans better in quality than the upper part.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2010 Then, when the next output scan is started, you have a choice of what target
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2011 scan number to use. The recommended choice is to use the current input scan
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2012 number at that time, which implies that you've skipped the output scans
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2013 corresponding to the input scans that were completed while you processed the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2014 previous output scan. In this way, the decoder automatically adapts its
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2015 speed to the arriving data, by skipping output scans as necessary to keep up
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2016 with the arriving data.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2017
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2018 When using this strategy, you'll want to be sure that you perform a final
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2019 output pass after receiving all the data; otherwise your last display may not
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2020 be full quality across the whole screen. So the right outer loop logic is
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2021 something like this:
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2022 do {
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2023 absorb any waiting input by calling jpeg_consume_input()
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2024 final_pass = jpeg_input_complete(&cinfo);
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2025 adjust output decompression parameters if required
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2026 jpeg_start_output(&cinfo, cinfo.input_scan_number);
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2027 ...
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2028 jpeg_finish_output()
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2029 } while (! final_pass);
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2030 rather than quitting as soon as jpeg_input_complete() returns TRUE. This
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2031 arrangement makes it simple to use higher-quality decoding parameters
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2032 for the final pass. But if you don't want to use special parameters for
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2033 the final pass, the right loop logic is like this:
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2034 for (;;) {
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2035 absorb any waiting input by calling jpeg_consume_input()
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2036 jpeg_start_output(&cinfo, cinfo.input_scan_number);
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2037 ...
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2038 jpeg_finish_output()
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2039 if (jpeg_input_complete(&cinfo) &&
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2040 cinfo.input_scan_number == cinfo.output_scan_number)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2041 break;
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2042 }
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2043 In this case you don't need to know in advance whether an output pass is to
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2044 be the last one, so it's not necessary to have reached EOF before starting
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2045 the final output pass; rather, what you want to test is whether the output
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2046 pass was performed in sync with the final input scan. This form of the loop
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2047 will avoid an extra output pass whenever the decoder is able (or nearly able)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2048 to keep up with the incoming data.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2049
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2050 When the data transmission speed is high, you might begin a display pass,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2051 then find that much or all of the file has arrived before you can complete
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2052 the pass. (You can detect this by noting the JPEG_REACHED_EOI return code
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2053 from jpeg_consume_input(), or equivalently by testing jpeg_input_complete().)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2054 In this situation you may wish to abort the current display pass and start a
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2055 new one using the newly arrived information. To do so, just call
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2056 jpeg_finish_output() and then start a new pass with jpeg_start_output().
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2057
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2058 A variant strategy is to abort and restart display if more than one complete
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2059 scan arrives during an output pass; this can be detected by noting
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2060 JPEG_REACHED_SOS returns and/or examining cinfo.input_scan_number. This
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2061 idea should be employed with caution, however, since the display process
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2062 might never get to the bottom of the image before being aborted, resulting
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2063 in the lower part of the screen being several passes worse than the upper.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2064 In most cases it's probably best to abort an output pass only if the whole
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2065 file has arrived and you want to begin the final output pass immediately.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2066
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2067 When receiving data across a communication link, we recommend always using
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2068 the current input scan number for the output target scan number; if a
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2069 higher-quality final pass is to be done, it should be started (aborting any
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2070 incomplete output pass) as soon as the end of file is received. However,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2071 many other strategies are possible. For example, the application can examine
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2072 the parameters of the current input scan and decide whether to display it or
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2073 not. If the scan contains only chroma data, one might choose not to use it
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2074 as the target scan, expecting that the scan will be small and will arrive
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2075 quickly. To skip to the next scan, call jpeg_consume_input() until it
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2076 returns JPEG_REACHED_SOS or JPEG_REACHED_EOI. Or just use the next higher
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2077 number as the target scan for jpeg_start_output(); but that method doesn't
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2078 let you inspect the next scan's parameters before deciding to display it.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2079
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2080
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2081 In buffered-image mode, jpeg_start_decompress() never performs input and
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2082 thus never suspends. An application that uses input suspension with
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2083 buffered-image mode must be prepared for suspension returns from these
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2084 routines:
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2085 * jpeg_start_output() performs input only if you request 2-pass quantization
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2086 and the target scan isn't fully read yet. (This is discussed below.)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2087 * jpeg_read_scanlines(), as always, returns the number of scanlines that it
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2088 was able to produce before suspending.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2089 * jpeg_finish_output() will read any markers following the target scan,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2090 up to the end of the file or the SOS marker that begins another scan.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2091 (But it reads no input if jpeg_consume_input() has already reached the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2092 end of the file or a SOS marker beyond the target output scan.)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2093 * jpeg_finish_decompress() will read until the end of file, and thus can
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2094 suspend if the end hasn't already been reached (as can be tested by
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2095 calling jpeg_input_complete()).
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2096 jpeg_start_output(), jpeg_finish_output(), and jpeg_finish_decompress()
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2097 all return TRUE if they completed their tasks, FALSE if they had to suspend.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2098 In the event of a FALSE return, the application must load more input data
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2099 and repeat the call. Applications that use non-suspending data sources need
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2100 not check the return values of these three routines.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2101
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2102
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2103 It is possible to change decoding parameters between output passes in the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2104 buffered-image mode. The decoder library currently supports only very
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2105 limited changes of parameters. ONLY THE FOLLOWING parameter changes are
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2106 allowed after jpeg_start_decompress() is called:
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2107 * dct_method can be changed before each call to jpeg_start_output().
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2108 For example, one could use a fast DCT method for early scans, changing
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2109 to a higher quality method for the final scan.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2110 * dither_mode can be changed before each call to jpeg_start_output();
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2111 of course this has no impact if not using color quantization. Typically
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2112 one would use ordered dither for initial passes, then switch to
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2113 Floyd-Steinberg dither for the final pass. Caution: changing dither mode
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2114 can cause more memory to be allocated by the library. Although the amount
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2115 of memory involved is not large (a scanline or so), it may cause the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2116 initial max_memory_to_use specification to be exceeded, which in the worst
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2117 case would result in an out-of-memory failure.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2118 * do_block_smoothing can be changed before each call to jpeg_start_output().
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2119 This setting is relevant only when decoding a progressive JPEG image.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2120 During the first DC-only scan, block smoothing provides a very "fuzzy" look
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2121 instead of the very "blocky" look seen without it; which is better seems a
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2122 matter of personal taste. But block smoothing is nearly always a win
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2123 during later stages, especially when decoding a successive-approximation
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2124 image: smoothing helps to hide the slight blockiness that otherwise shows
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2125 up on smooth gradients until the lowest coefficient bits are sent.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2126 * Color quantization mode can be changed under the rules described below.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2127 You cannot change between full-color and quantized output (because that
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2128 would alter the required I/O buffer sizes), but you can change which
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2129 quantization method is used.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2130
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2131 When generating color-quantized output, changing quantization method is a
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2132 very useful way of switching between high-speed and high-quality display.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2133 The library allows you to change among its three quantization methods:
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2134 1. Single-pass quantization to a fixed color cube.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2135 Selected by cinfo.two_pass_quantize = FALSE and cinfo.colormap = NULL.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2136 2. Single-pass quantization to an application-supplied colormap.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2137 Selected by setting cinfo.colormap to point to the colormap (the value of
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2138 two_pass_quantize is ignored); also set cinfo.actual_number_of_colors.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2139 3. Two-pass quantization to a colormap chosen specifically for the image.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2140 Selected by cinfo.two_pass_quantize = TRUE and cinfo.colormap = NULL.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2141 (This is the default setting selected by jpeg_read_header, but it is
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2142 probably NOT what you want for the first pass of progressive display!)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2143 These methods offer successively better quality and lesser speed. However,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2144 only the first method is available for quantizing in non-RGB color spaces.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2145
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2146 IMPORTANT: because the different quantizer methods have very different
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2147 working-storage requirements, the library requires you to indicate which
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2148 one(s) you intend to use before you call jpeg_start_decompress(). (If we did
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2149 not require this, the max_memory_to_use setting would be a complete fiction.)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2150 You do this by setting one or more of these three cinfo fields to TRUE:
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2151 enable_1pass_quant Fixed color cube colormap
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2152 enable_external_quant Externally-supplied colormap
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2153 enable_2pass_quant Two-pass custom colormap
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2154 All three are initialized FALSE by jpeg_read_header(). But
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2155 jpeg_start_decompress() automatically sets TRUE the one selected by the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2156 current two_pass_quantize and colormap settings, so you only need to set the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2157 enable flags for any other quantization methods you plan to change to later.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2158
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2159 After setting the enable flags correctly at jpeg_start_decompress() time, you
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2160 can change to any enabled quantization method by setting two_pass_quantize
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2161 and colormap properly just before calling jpeg_start_output(). The following
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2162 special rules apply:
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2163 1. You must explicitly set cinfo.colormap to NULL when switching to 1-pass
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2164 or 2-pass mode from a different mode, or when you want the 2-pass
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2165 quantizer to be re-run to generate a new colormap.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2166 2. To switch to an external colormap, or to change to a different external
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2167 colormap than was used on the prior pass, you must call
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2168 jpeg_new_colormap() after setting cinfo.colormap.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2169 NOTE: if you want to use the same colormap as was used in the prior pass,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2170 you should not do either of these things. This will save some nontrivial
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2171 switchover costs.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2172 (These requirements exist because cinfo.colormap will always be non-NULL
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2173 after completing a prior output pass, since both the 1-pass and 2-pass
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2174 quantizers set it to point to their output colormaps. Thus you have to
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2175 do one of these two things to notify the library that something has changed.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2176 Yup, it's a bit klugy, but it's necessary to do it this way for backwards
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2177 compatibility.)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2178
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2179 Note that in buffered-image mode, the library generates any requested colormap
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2180 during jpeg_start_output(), not during jpeg_start_decompress().
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2181
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2182 When using two-pass quantization, jpeg_start_output() makes a pass over the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2183 buffered image to determine the optimum color map; it therefore may take a
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2184 significant amount of time, whereas ordinarily it does little work. The
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2185 progress monitor hook is called during this pass, if defined. It is also
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2186 important to realize that if the specified target scan number is greater than
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2187 or equal to the current input scan number, jpeg_start_output() will attempt
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2188 to consume input as it makes this pass. If you use a suspending data source,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2189 you need to check for a FALSE return from jpeg_start_output() under these
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2190 conditions. The combination of 2-pass quantization and a not-yet-fully-read
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2191 target scan is the only case in which jpeg_start_output() will consume input.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2192
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2193
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2194 Application authors who support buffered-image mode may be tempted to use it
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2195 for all JPEG images, even single-scan ones. This will work, but it is
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2196 inefficient: there is no need to create an image-sized coefficient buffer for
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2197 single-scan images. Requesting buffered-image mode for such an image wastes
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2198 memory. Worse, it can cost time on large images, since the buffered data has
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2199 to be swapped out or written to a temporary file. If you are concerned about
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2200 maximum performance on baseline JPEG files, you should use buffered-image
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2201 mode only when the incoming file actually has multiple scans. This can be
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2202 tested by calling jpeg_has_multiple_scans(), which will return a correct
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2203 result at any time after jpeg_read_header() completes.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2204
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2205 It is also worth noting that when you use jpeg_consume_input() to let input
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2206 processing get ahead of output processing, the resulting pattern of access to
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2207 the coefficient buffer is quite nonsequential. It's best to use the memory
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2208 manager jmemnobs.c if you can (ie, if you have enough real or virtual main
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2209 memory). If not, at least make sure that max_memory_to_use is set as high as
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2210 possible. If the JPEG memory manager has to use a temporary file, you will
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2211 probably see a lot of disk traffic and poor performance. (This could be
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2212 improved with additional work on the memory manager, but we haven't gotten
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2213 around to it yet.)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2214
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2215 In some applications it may be convenient to use jpeg_consume_input() for all
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2216 input processing, including reading the initial markers; that is, you may
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2217 wish to call jpeg_consume_input() instead of jpeg_read_header() during
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2218 startup. This works, but note that you must check for JPEG_REACHED_SOS and
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2219 JPEG_REACHED_EOI return codes as the equivalent of jpeg_read_header's codes.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2220 Once the first SOS marker has been reached, you must call
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2221 jpeg_start_decompress() before jpeg_consume_input() will consume more input;
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2222 it'll just keep returning JPEG_REACHED_SOS until you do. If you read a
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2223 tables-only file this way, jpeg_consume_input() will return JPEG_REACHED_EOI
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2224 without ever returning JPEG_REACHED_SOS; be sure to check for this case.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2225 If this happens, the decompressor will not read any more input until you call
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2226 jpeg_abort() to reset it. It is OK to call jpeg_consume_input() even when not
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2227 using buffered-image mode, but in that case it's basically a no-op after the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2228 initial markers have been read: it will just return JPEG_SUSPENDED.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2229
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2230
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2231 Abbreviated datastreams and multiple images
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2232 -------------------------------------------
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2233
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2234 A JPEG compression or decompression object can be reused to process multiple
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2235 images. This saves a small amount of time per image by eliminating the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2236 "create" and "destroy" operations, but that isn't the real purpose of the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2237 feature. Rather, reuse of an object provides support for abbreviated JPEG
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2238 datastreams. Object reuse can also simplify processing a series of images in
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2239 a single input or output file. This section explains these features.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2240
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2241 A JPEG file normally contains several hundred bytes worth of quantization
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2242 and Huffman tables. In a situation where many images will be stored or
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2243 transmitted with identical tables, this may represent an annoying overhead.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2244 The JPEG standard therefore permits tables to be omitted. The standard
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2245 defines three classes of JPEG datastreams:
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2246 * "Interchange" datastreams contain an image and all tables needed to decode
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2247 the image. These are the usual kind of JPEG file.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2248 * "Abbreviated image" datastreams contain an image, but are missing some or
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2249 all of the tables needed to decode that image.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2250 * "Abbreviated table specification" (henceforth "tables-only") datastreams
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2251 contain only table specifications.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2252 To decode an abbreviated image, it is necessary to load the missing table(s)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2253 into the decoder beforehand. This can be accomplished by reading a separate
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2254 tables-only file. A variant scheme uses a series of images in which the first
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2255 image is an interchange (complete) datastream, while subsequent ones are
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2256 abbreviated and rely on the tables loaded by the first image. It is assumed
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2257 that once the decoder has read a table, it will remember that table until a
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2258 new definition for the same table number is encountered.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2259
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2260 It is the application designer's responsibility to figure out how to associate
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2261 the correct tables with an abbreviated image. While abbreviated datastreams
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2262 can be useful in a closed environment, their use is strongly discouraged in
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2263 any situation where data exchange with other applications might be needed.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2264 Caveat designer.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2265
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2266 The JPEG library provides support for reading and writing any combination of
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2267 tables-only datastreams and abbreviated images. In both compression and
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2268 decompression objects, a quantization or Huffman table will be retained for
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2269 the lifetime of the object, unless it is overwritten by a new table definition.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2270
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2271
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2272 To create abbreviated image datastreams, it is only necessary to tell the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2273 compressor not to emit some or all of the tables it is using. Each
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2274 quantization and Huffman table struct contains a boolean field "sent_table",
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2275 which normally is initialized to FALSE. For each table used by the image, the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2276 header-writing process emits the table and sets sent_table = TRUE unless it is
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2277 already TRUE. (In normal usage, this prevents outputting the same table
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2278 definition multiple times, as would otherwise occur because the chroma
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2279 components typically share tables.) Thus, setting this field to TRUE before
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2280 calling jpeg_start_compress() will prevent the table from being written at
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2281 all.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2282
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2283 If you want to create a "pure" abbreviated image file containing no tables,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2284 just call "jpeg_suppress_tables(&cinfo, TRUE)" after constructing all the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2285 tables. If you want to emit some but not all tables, you'll need to set the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2286 individual sent_table fields directly.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2287
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2288 To create an abbreviated image, you must also call jpeg_start_compress()
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2289 with a second parameter of FALSE, not TRUE. Otherwise jpeg_start_compress()
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2290 will force all the sent_table fields to FALSE. (This is a safety feature to
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2291 prevent abbreviated images from being created accidentally.)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2292
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2293 To create a tables-only file, perform the same parameter setup that you
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2294 normally would, but instead of calling jpeg_start_compress() and so on, call
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2295 jpeg_write_tables(&cinfo). This will write an abbreviated datastream
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2296 containing only SOI, DQT and/or DHT markers, and EOI. All the quantization
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2297 and Huffman tables that are currently defined in the compression object will
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2298 be emitted unless their sent_tables flag is already TRUE, and then all the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2299 sent_tables flags will be set TRUE.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2300
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2301 A sure-fire way to create matching tables-only and abbreviated image files
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2302 is to proceed as follows:
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2303
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2304 create JPEG compression object
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2305 set JPEG parameters
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2306 set destination to tables-only file
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2307 jpeg_write_tables(&cinfo);
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2308 set destination to image file
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2309 jpeg_start_compress(&cinfo, FALSE);
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2310 write data...
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2311 jpeg_finish_compress(&cinfo);
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2312
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2313 Since the JPEG parameters are not altered between writing the table file and
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2314 the abbreviated image file, the same tables are sure to be used. Of course,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2315 you can repeat the jpeg_start_compress() ... jpeg_finish_compress() sequence
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2316 many times to produce many abbreviated image files matching the table file.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2317
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2318 You cannot suppress output of the computed Huffman tables when Huffman
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2319 optimization is selected. (If you could, there'd be no way to decode the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2320 image...) Generally, you don't want to set optimize_coding = TRUE when
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2321 you are trying to produce abbreviated files.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2322
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2323 In some cases you might want to compress an image using tables which are
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2324 not stored in the application, but are defined in an interchange or
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2325 tables-only file readable by the application. This can be done by setting up
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2326 a JPEG decompression object to read the specification file, then copying the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2327 tables into your compression object. See jpeg_copy_critical_parameters()
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2328 for an example of copying quantization tables.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2329
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2330
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2331 To read abbreviated image files, you simply need to load the proper tables
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2332 into the decompression object before trying to read the abbreviated image.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2333 If the proper tables are stored in the application program, you can just
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2334 allocate the table structs and fill in their contents directly. For example,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2335 to load a fixed quantization table into table slot "n":
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2336
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2337 if (cinfo.quant_tbl_ptrs[n] == NULL)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2338 cinfo.quant_tbl_ptrs[n] = jpeg_alloc_quant_table((j_common_ptr) &cinfo);
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2339 quant_ptr = cinfo.quant_tbl_ptrs[n]; /* quant_ptr is JQUANT_TBL* */
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2340 for (i = 0; i < 64; i++) {
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2341 /* Qtable[] is desired quantization table, in natural array order */
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2342 quant_ptr->quantval[i] = Qtable[i];
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2343 }
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2344
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2345 Code to load a fixed Huffman table is typically (for AC table "n"):
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2346
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2347 if (cinfo.ac_huff_tbl_ptrs[n] == NULL)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2348 cinfo.ac_huff_tbl_ptrs[n] = jpeg_alloc_huff_table((j_common_ptr) &cinfo);
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2349 huff_ptr = cinfo.ac_huff_tbl_ptrs[n]; /* huff_ptr is JHUFF_TBL* */
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2350 for (i = 1; i <= 16; i++) {
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2351 /* counts[i] is number of Huffman codes of length i bits, i=1..16 */
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2352 huff_ptr->bits[i] = counts[i];
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2353 }
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2354 for (i = 0; i < 256; i++) {
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2355 /* symbols[] is the list of Huffman symbols, in code-length order */
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2356 huff_ptr->huffval[i] = symbols[i];
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2357 }
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2358
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2359 (Note that trying to set cinfo.quant_tbl_ptrs[n] to point directly at a
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2360 constant JQUANT_TBL object is not safe. If the incoming file happened to
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2361 contain a quantization table definition, your master table would get
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2362 overwritten! Instead allocate a working table copy and copy the master table
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2363 into it, as illustrated above. Ditto for Huffman tables, of course.)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2364
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2365 You might want to read the tables from a tables-only file, rather than
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2366 hard-wiring them into your application. The jpeg_read_header() call is
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2367 sufficient to read a tables-only file. You must pass a second parameter of
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2368 FALSE to indicate that you do not require an image to be present. Thus, the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2369 typical scenario is
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2370
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2371 create JPEG decompression object
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2372 set source to tables-only file
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2373 jpeg_read_header(&cinfo, FALSE);
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2374 set source to abbreviated image file
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2375 jpeg_read_header(&cinfo, TRUE);
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2376 set decompression parameters
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2377 jpeg_start_decompress(&cinfo);
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2378 read data...
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2379 jpeg_finish_decompress(&cinfo);
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2380
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2381 In some cases, you may want to read a file without knowing whether it contains
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2382 an image or just tables. In that case, pass FALSE and check the return value
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2383 from jpeg_read_header(): it will be JPEG_HEADER_OK if an image was found,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2384 JPEG_HEADER_TABLES_ONLY if only tables were found. (A third return value,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2385 JPEG_SUSPENDED, is possible when using a suspending data source manager.)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2386 Note that jpeg_read_header() will not complain if you read an abbreviated
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2387 image for which you haven't loaded the missing tables; the missing-table check
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2388 occurs later, in jpeg_start_decompress().
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2389
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2390
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2391 It is possible to read a series of images from a single source file by
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2392 repeating the jpeg_read_header() ... jpeg_finish_decompress() sequence,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2393 without releasing/recreating the JPEG object or the data source module.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2394 (If you did reinitialize, any partial bufferload left in the data source
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2395 buffer at the end of one image would be discarded, causing you to lose the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2396 start of the next image.) When you use this method, stored tables are
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2397 automatically carried forward, so some of the images can be abbreviated images
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2398 that depend on tables from earlier images.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2399
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2400 If you intend to write a series of images into a single destination file,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2401 you might want to make a specialized data destination module that doesn't
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2402 flush the output buffer at term_destination() time. This would speed things
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2403 up by some trifling amount. Of course, you'd need to remember to flush the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2404 buffer after the last image. You can make the later images be abbreviated
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2405 ones by passing FALSE to jpeg_start_compress().
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2406
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2407
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2408 Special markers
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2409 ---------------
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2410
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2411 Some applications may need to insert or extract special data in the JPEG
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2412 datastream. The JPEG standard provides marker types "COM" (comment) and
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2413 "APP0" through "APP15" (application) to hold application-specific data.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2414 Unfortunately, the use of these markers is not specified by the standard.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2415 COM markers are fairly widely used to hold user-supplied text. The JFIF file
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2416 format spec uses APP0 markers with specified initial strings to hold certain
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2417 data. Adobe applications use APP14 markers beginning with the string "Adobe"
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2418 for miscellaneous data. Other APPn markers are rarely seen, but might
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2419 contain almost anything.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2420
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2421 If you wish to store user-supplied text, we recommend you use COM markers
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2422 and place readable 7-bit ASCII text in them. Newline conventions are not
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2423 standardized --- expect to find LF (Unix style), CR/LF (DOS style), or CR
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2424 (Mac style). A robust COM reader should be able to cope with random binary
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2425 garbage, including nulls, since some applications generate COM markers
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2426 containing non-ASCII junk. (But yours should not be one of them.)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2427
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2428 For program-supplied data, use an APPn marker, and be sure to begin it with an
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2429 identifying string so that you can tell whether the marker is actually yours.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2430 It's probably best to avoid using APP0 or APP14 for any private markers.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2431 (NOTE: the upcoming SPIFF standard will use APP8 markers; we recommend you
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2432 not use APP8 markers for any private purposes, either.)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2433
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2434 Keep in mind that at most 65533 bytes can be put into one marker, but you
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2435 can have as many markers as you like.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2436
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2437 By default, the IJG compression library will write a JFIF APP0 marker if the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2438 selected JPEG colorspace is grayscale or YCbCr, or an Adobe APP14 marker if
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2439 the selected colorspace is RGB, CMYK, or YCCK. You can disable this, but
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2440 we don't recommend it. The decompression library will recognize JFIF and
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2441 Adobe markers and will set the JPEG colorspace properly when one is found.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2442
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2443
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2444 You can write special markers immediately following the datastream header by
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2445 calling jpeg_write_marker() after jpeg_start_compress() and before the first
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2446 call to jpeg_write_scanlines(). When you do this, the markers appear after
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2447 the SOI and the JFIF APP0 and Adobe APP14 markers (if written), but before
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2448 all else. Specify the marker type parameter as "JPEG_COM" for COM or
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2449 "JPEG_APP0 + n" for APPn. (Actually, jpeg_write_marker will let you write
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2450 any marker type, but we don't recommend writing any other kinds of marker.)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2451 For example, to write a user comment string pointed to by comment_text:
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2452 jpeg_write_marker(cinfo, JPEG_COM, comment_text, strlen(comment_text));
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2453
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2454 If it's not convenient to store all the marker data in memory at once,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2455 you can instead call jpeg_write_m_header() followed by multiple calls to
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2456 jpeg_write_m_byte(). If you do it this way, it's your responsibility to
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2457 call jpeg_write_m_byte() exactly the number of times given in the length
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2458 parameter to jpeg_write_m_header(). (This method lets you empty the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2459 output buffer partway through a marker, which might be important when
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2460 using a suspending data destination module. In any case, if you are using
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2461 a suspending destination, you should flush its buffer after inserting
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2462 any special markers. See "I/O suspension".)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2463
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2464 Or, if you prefer to synthesize the marker byte sequence yourself,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2465 you can just cram it straight into the data destination module.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2466
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2467 If you are writing JFIF 1.02 extension markers (thumbnail images), don't
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2468 forget to set cinfo.JFIF_minor_version = 2 so that the encoder will write the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2469 correct JFIF version number in the JFIF header marker. The library's default
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2470 is to write version 1.01, but that's wrong if you insert any 1.02 extension
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2471 markers. (We could probably get away with just defaulting to 1.02, but there
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2472 used to be broken decoders that would complain about unknown minor version
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2473 numbers. To reduce compatibility risks it's safest not to write 1.02 unless
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2474 you are actually using 1.02 extensions.)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2475
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2476
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2477 When reading, two methods of handling special markers are available:
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2478 1. You can ask the library to save the contents of COM and/or APPn markers
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2479 into memory, and then examine them at your leisure afterwards.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2480 2. You can supply your own routine to process COM and/or APPn markers
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2481 on-the-fly as they are read.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2482 The first method is simpler to use, especially if you are using a suspending
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2483 data source; writing a marker processor that copes with input suspension is
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2484 not easy (consider what happens if the marker is longer than your available
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2485 input buffer). However, the second method conserves memory since the marker
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2486 data need not be kept around after it's been processed.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2487
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2488 For either method, you'd normally set up marker handling after creating a
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2489 decompression object and before calling jpeg_read_header(), because the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2490 markers of interest will typically be near the head of the file and so will
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2491 be scanned by jpeg_read_header. Once you've established a marker handling
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2492 method, it will be used for the life of that decompression object
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2493 (potentially many datastreams), unless you change it. Marker handling is
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2494 determined separately for COM markers and for each APPn marker code.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2495
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2496
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2497 To save the contents of special markers in memory, call
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2498 jpeg_save_markers(cinfo, marker_code, length_limit)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2499 where marker_code is the marker type to save, JPEG_COM or JPEG_APP0+n.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2500 (To arrange to save all the special marker types, you need to call this
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2501 routine 17 times, for COM and APP0-APP15.) If the incoming marker is longer
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2502 than length_limit data bytes, only length_limit bytes will be saved; this
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2503 parameter allows you to avoid chewing up memory when you only need to see the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2504 first few bytes of a potentially large marker. If you want to save all the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2505 data, set length_limit to 0xFFFF; that is enough since marker lengths are only
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2506 16 bits. As a special case, setting length_limit to 0 prevents that marker
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2507 type from being saved at all. (That is the default behavior, in fact.)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2508
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2509 After jpeg_read_header() completes, you can examine the special markers by
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2510 following the cinfo->marker_list pointer chain. All the special markers in
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2511 the file appear in this list, in order of their occurrence in the file (but
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2512 omitting any markers of types you didn't ask for). Both the original data
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2513 length and the saved data length are recorded for each list entry; the latter
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2514 will not exceed length_limit for the particular marker type. Note that these
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2515 lengths exclude the marker length word, whereas the stored representation
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2516 within the JPEG file includes it. (Hence the maximum data length is really
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2517 only 65533.)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2518
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2519 It is possible that additional special markers appear in the file beyond the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2520 SOS marker at which jpeg_read_header stops; if so, the marker list will be
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2521 extended during reading of the rest of the file. This is not expected to be
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2522 common, however. If you are short on memory you may want to reset the length
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2523 limit to zero for all marker types after finishing jpeg_read_header, to
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2524 ensure that the max_memory_to_use setting cannot be exceeded due to addition
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2525 of later markers.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2526
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2527 The marker list remains stored until you call jpeg_finish_decompress or
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2528 jpeg_abort, at which point the memory is freed and the list is set to empty.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2529 (jpeg_destroy also releases the storage, of course.)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2530
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2531 Note that the library is internally interested in APP0 and APP14 markers;
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2532 if you try to set a small nonzero length limit on these types, the library
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2533 will silently force the length up to the minimum it wants. (But you can set
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2534 a zero length limit to prevent them from being saved at all.) Also, in a
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2535 16-bit environment, the maximum length limit may be constrained to less than
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2536 65533 by malloc() limitations. It is therefore best not to assume that the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2537 effective length limit is exactly what you set it to be.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2538
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2539
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2540 If you want to supply your own marker-reading routine, you do it by calling
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2541 jpeg_set_marker_processor(). A marker processor routine must have the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2542 signature
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2543 boolean jpeg_marker_parser_method (j_decompress_ptr cinfo)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2544 Although the marker code is not explicitly passed, the routine can find it
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2545 in cinfo->unread_marker. At the time of call, the marker proper has been
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2546 read from the data source module. The processor routine is responsible for
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2547 reading the marker length word and the remaining parameter bytes, if any.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2548 Return TRUE to indicate success. (FALSE should be returned only if you are
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2549 using a suspending data source and it tells you to suspend. See the standard
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2550 marker processors in jdmarker.c for appropriate coding methods if you need to
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2551 use a suspending data source.)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2552
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2553 If you override the default APP0 or APP14 processors, it is up to you to
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2554 recognize JFIF and Adobe markers if you want colorspace recognition to occur
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2555 properly. We recommend copying and extending the default processors if you
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2556 want to do that. (A better idea is to save these marker types for later
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2557 examination by calling jpeg_save_markers(); that method doesn't interfere
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2558 with the library's own processing of these markers.)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2559
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2560 jpeg_set_marker_processor() and jpeg_save_markers() are mutually exclusive
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2561 --- if you call one it overrides any previous call to the other, for the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2562 particular marker type specified.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2563
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2564 A simple example of an external COM processor can be found in djpeg.c.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2565 Also, see jpegtran.c for an example of using jpeg_save_markers.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2566
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2567
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2568 Raw (downsampled) image data
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2569 ----------------------------
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2570
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2571 Some applications need to supply already-downsampled image data to the JPEG
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2572 compressor, or to receive raw downsampled data from the decompressor. The
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2573 library supports this requirement by allowing the application to write or
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2574 read raw data, bypassing the normal preprocessing or postprocessing steps.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2575 The interface is different from the standard one and is somewhat harder to
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2576 use. If your interest is merely in bypassing color conversion, we recommend
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2577 that you use the standard interface and simply set jpeg_color_space =
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2578 in_color_space (or jpeg_color_space = out_color_space for decompression).
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2579 The mechanism described in this section is necessary only to supply or
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2580 receive downsampled image data, in which not all components have the same
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2581 dimensions.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2582
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2583
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2584 To compress raw data, you must supply the data in the colorspace to be used
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2585 in the JPEG file (please read the earlier section on Special color spaces)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2586 and downsampled to the sampling factors specified in the JPEG parameters.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2587 You must supply the data in the format used internally by the JPEG library,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2588 namely a JSAMPIMAGE array. This is an array of pointers to two-dimensional
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2589 arrays, each of type JSAMPARRAY. Each 2-D array holds the values for one
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2590 color component. This structure is necessary since the components are of
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2591 different sizes. If the image dimensions are not a multiple of the MCU size,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2592 you must also pad the data correctly (usually, this is done by replicating
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2593 the last column and/or row). The data must be padded to a multiple of a DCT
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2594 block in each component: that is, each downsampled row must contain a
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2595 multiple of DCT_h_scaled_size valid samples, and there must be a multiple of
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2596 DCT_v_scaled_size sample rows for each component. (For applications such as
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2597 conversion of digital TV images, the standard image size is usually a
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2598 multiple of the DCT block size, so that no padding need actually be done.)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2599
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2600 The procedure for compression of raw data is basically the same as normal
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2601 compression, except that you call jpeg_write_raw_data() in place of
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2602 jpeg_write_scanlines(). Before calling jpeg_start_compress(), you must do
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2603 the following:
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2604 * Set cinfo->raw_data_in to TRUE. (It is set FALSE by jpeg_set_defaults().)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2605 This notifies the library that you will be supplying raw data.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2606 * Ensure jpeg_color_space is correct --- an explicit jpeg_set_colorspace()
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2607 call is a good idea. Note that since color conversion is bypassed,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2608 in_color_space is ignored, except that jpeg_set_defaults() uses it to
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2609 choose the default jpeg_color_space setting.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2610 * Ensure the sampling factors, cinfo->comp_info[i].h_samp_factor and
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2611 cinfo->comp_info[i].v_samp_factor, are correct. Since these indicate the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2612 dimensions of the data you are supplying, it's wise to set them
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2613 explicitly, rather than assuming the library's defaults are what you want.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2614
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2615 To pass raw data to the library, call jpeg_write_raw_data() in place of
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2616 jpeg_write_scanlines(). The two routines work similarly except that
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2617 jpeg_write_raw_data takes a JSAMPIMAGE data array rather than JSAMPARRAY.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2618 The scanlines count passed to and returned from jpeg_write_raw_data is
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2619 measured in terms of the component with the largest v_samp_factor.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2620
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2621 jpeg_write_raw_data() processes one MCU row per call, which is to say
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2622 v_samp_factor*min_DCT_v_scaled_size sample rows of each component. The passed
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2623 num_lines value must be at least max_v_samp_factor*min_DCT_v_scaled_size, and
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2624 the return value will be exactly that amount (or possibly some multiple of
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2625 that amount, in future library versions). This is true even on the last call
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2626 at the bottom of the image; don't forget to pad your data as necessary.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2627
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2628 The required dimensions of the supplied data can be computed for each
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2629 component as
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2630 cinfo->comp_info[i].width_in_blocks *
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2631 cinfo->comp_info[i].DCT_h_scaled_size samples per row
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2632 cinfo->comp_info[i].height_in_blocks *
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2633 cinfo->comp_info[i].DCT_v_scaled_size rows in image
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2634 after jpeg_start_compress() has initialized those fields. If the valid data
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2635 is smaller than this, it must be padded appropriately. For some sampling
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2636 factors and image sizes, additional dummy DCT blocks are inserted to make
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2637 the image a multiple of the MCU dimensions. The library creates such dummy
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2638 blocks itself; it does not read them from your supplied data. Therefore you
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2639 need never pad by more than DCT_scaled_size samples.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2640 An example may help here. Assume 2h2v downsampling of YCbCr data, that is
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2641 cinfo->comp_info[0].h_samp_factor = 2 for Y
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2642 cinfo->comp_info[0].v_samp_factor = 2
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2643 cinfo->comp_info[1].h_samp_factor = 1 for Cb
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2644 cinfo->comp_info[1].v_samp_factor = 1
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2645 cinfo->comp_info[2].h_samp_factor = 1 for Cr
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2646 cinfo->comp_info[2].v_samp_factor = 1
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2647 and suppose that the nominal image dimensions (cinfo->image_width and
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2648 cinfo->image_height) are 101x101 pixels. Then jpeg_start_compress() will
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2649 compute downsampled_width = 101 and width_in_blocks = 13 for Y,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2650 downsampled_width = 51 and width_in_blocks = 7 for Cb and Cr (and the same
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2651 for the height fields). You must pad the Y data to at least 13*8 = 104
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2652 columns and rows, the Cb/Cr data to at least 7*8 = 56 columns and rows. The
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2653 MCU height is max_v_samp_factor = 2 DCT rows so you must pass at least 16
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2654 scanlines on each call to jpeg_write_raw_data(), which is to say 16 actual
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2655 sample rows of Y and 8 each of Cb and Cr. A total of 7 MCU rows are needed,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2656 so you must pass a total of 7*16 = 112 "scanlines". The last DCT block row
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2657 of Y data is dummy, so it doesn't matter what you pass for it in the data
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2658 arrays, but the scanlines count must total up to 112 so that all of the Cb
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2659 and Cr data gets passed.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2660
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2661 Output suspension is supported with raw-data compression: if the data
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2662 destination module suspends, jpeg_write_raw_data() will return 0.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2663 In this case the same data rows must be passed again on the next call.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2664
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2665
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2666 Decompression with raw data output implies bypassing all postprocessing:
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2667 you cannot ask for color quantization, for instance. More seriously, you
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2668 must deal with the color space and sampling factors present in the incoming
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2669 file. If your application only handles, say, 2h1v YCbCr data, you must
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2670 check for and fail on other color spaces or other sampling factors.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2671 The library will not convert to a different color space for you.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2672
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2673 To obtain raw data output, set cinfo->raw_data_out = TRUE before
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2674 jpeg_start_decompress() (it is set FALSE by jpeg_read_header()). Be sure to
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2675 verify that the color space and sampling factors are ones you can handle.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2676 Then call jpeg_read_raw_data() in place of jpeg_read_scanlines(). The
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2677 decompression process is otherwise the same as usual.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2678
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2679 jpeg_read_raw_data() returns one MCU row per call, and thus you must pass a
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2680 buffer of at least max_v_samp_factor*min_DCT_v_scaled_size scanlines (scanline
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2681 counting is the same as for raw-data compression). The buffer you pass must
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2682 be large enough to hold the actual data plus padding to DCT-block boundaries.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2683 As with compression, any entirely dummy DCT blocks are not processed so you
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2684 need not allocate space for them, but the total scanline count includes them.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2685 The above example of computing buffer dimensions for raw-data compression is
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2686 equally valid for decompression.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2687
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2688 Input suspension is supported with raw-data decompression: if the data source
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2689 module suspends, jpeg_read_raw_data() will return 0. You can also use
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2690 buffered-image mode to read raw data in multiple passes.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2691
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2692
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2693 Really raw data: DCT coefficients
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2694 ---------------------------------
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2695
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2696 It is possible to read or write the contents of a JPEG file as raw DCT
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2697 coefficients. This facility is mainly intended for use in lossless
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2698 transcoding between different JPEG file formats. Other possible applications
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2699 include lossless cropping of a JPEG image, lossless reassembly of a
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2700 multi-strip or multi-tile TIFF/JPEG file into a single JPEG datastream, etc.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2701
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2702 To read the contents of a JPEG file as DCT coefficients, open the file and do
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2703 jpeg_read_header() as usual. But instead of calling jpeg_start_decompress()
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2704 and jpeg_read_scanlines(), call jpeg_read_coefficients(). This will read the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2705 entire image into a set of virtual coefficient-block arrays, one array per
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2706 component. The return value is a pointer to an array of virtual-array
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2707 descriptors. Each virtual array can be accessed directly using the JPEG
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2708 memory manager's access_virt_barray method (see Memory management, below,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2709 and also read structure.txt's discussion of virtual array handling). Or,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2710 for simple transcoding to a different JPEG file format, the array list can
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2711 just be handed directly to jpeg_write_coefficients().
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2712
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2713 Each block in the block arrays contains quantized coefficient values in
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2714 normal array order (not JPEG zigzag order). The block arrays contain only
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2715 DCT blocks containing real data; any entirely-dummy blocks added to fill out
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2716 interleaved MCUs at the right or bottom edges of the image are discarded
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2717 during reading and are not stored in the block arrays. (The size of each
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2718 block array can be determined from the width_in_blocks and height_in_blocks
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2719 fields of the component's comp_info entry.) This is also the data format
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2720 expected by jpeg_write_coefficients().
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2721
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2722 When you are done using the virtual arrays, call jpeg_finish_decompress()
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2723 to release the array storage and return the decompression object to an idle
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2724 state; or just call jpeg_destroy() if you don't need to reuse the object.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2725
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2726 If you use a suspending data source, jpeg_read_coefficients() will return
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2727 NULL if it is forced to suspend; a non-NULL return value indicates successful
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2728 completion. You need not test for a NULL return value when using a
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2729 non-suspending data source.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2730
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2731 It is also possible to call jpeg_read_coefficients() to obtain access to the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2732 decoder's coefficient arrays during a normal decode cycle in buffered-image
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2733 mode. This frammish might be useful for progressively displaying an incoming
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2734 image and then re-encoding it without loss. To do this, decode in buffered-
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2735 image mode as discussed previously, then call jpeg_read_coefficients() after
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2736 the last jpeg_finish_output() call. The arrays will be available for your use
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2737 until you call jpeg_finish_decompress().
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2738
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2739
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2740 To write the contents of a JPEG file as DCT coefficients, you must provide
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2741 the DCT coefficients stored in virtual block arrays. You can either pass
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2742 block arrays read from an input JPEG file by jpeg_read_coefficients(), or
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2743 allocate virtual arrays from the JPEG compression object and fill them
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2744 yourself. In either case, jpeg_write_coefficients() is substituted for
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2745 jpeg_start_compress() and jpeg_write_scanlines(). Thus the sequence is
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2746 * Create compression object
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2747 * Set all compression parameters as necessary
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2748 * Request virtual arrays if needed
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2749 * jpeg_write_coefficients()
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2750 * jpeg_finish_compress()
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2751 * Destroy or re-use compression object
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2752 jpeg_write_coefficients() is passed a pointer to an array of virtual block
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2753 array descriptors; the number of arrays is equal to cinfo.num_components.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2754
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2755 The virtual arrays need only have been requested, not realized, before
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2756 jpeg_write_coefficients() is called. A side-effect of
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2757 jpeg_write_coefficients() is to realize any virtual arrays that have been
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2758 requested from the compression object's memory manager. Thus, when obtaining
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2759 the virtual arrays from the compression object, you should fill the arrays
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2760 after calling jpeg_write_coefficients(). The data is actually written out
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2761 when you call jpeg_finish_compress(); jpeg_write_coefficients() only writes
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2762 the file header.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2763
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2764 When writing raw DCT coefficients, it is crucial that the JPEG quantization
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2765 tables and sampling factors match the way the data was encoded, or the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2766 resulting file will be invalid. For transcoding from an existing JPEG file,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2767 we recommend using jpeg_copy_critical_parameters(). This routine initializes
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2768 all the compression parameters to default values (like jpeg_set_defaults()),
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2769 then copies the critical information from a source decompression object.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2770 The decompression object should have just been used to read the entire
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2771 JPEG input file --- that is, it should be awaiting jpeg_finish_decompress().
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2772
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2773 jpeg_write_coefficients() marks all tables stored in the compression object
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2774 as needing to be written to the output file (thus, it acts like
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2775 jpeg_start_compress(cinfo, TRUE)). This is for safety's sake, to avoid
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2776 emitting abbreviated JPEG files by accident. If you really want to emit an
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2777 abbreviated JPEG file, call jpeg_suppress_tables(), or set the tables'
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2778 individual sent_table flags, between calling jpeg_write_coefficients() and
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2779 jpeg_finish_compress().
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2780
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2781
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2782 Progress monitoring
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2783 -------------------
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2784
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2785 Some applications may need to regain control from the JPEG library every so
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2786 often. The typical use of this feature is to produce a percent-done bar or
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2787 other progress display. (For a simple example, see cjpeg.c or djpeg.c.)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2788 Although you do get control back frequently during the data-transferring pass
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2789 (the jpeg_read_scanlines or jpeg_write_scanlines loop), any additional passes
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2790 will occur inside jpeg_finish_compress or jpeg_start_decompress; those
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2791 routines may take a long time to execute, and you don't get control back
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2792 until they are done.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2793
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2794 You can define a progress-monitor routine which will be called periodically
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2795 by the library. No guarantees are made about how often this call will occur,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2796 so we don't recommend you use it for mouse tracking or anything like that.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2797 At present, a call will occur once per MCU row, scanline, or sample row
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2798 group, whichever unit is convenient for the current processing mode; so the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2799 wider the image, the longer the time between calls. During the data
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2800 transferring pass, only one call occurs per call of jpeg_read_scanlines or
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2801 jpeg_write_scanlines, so don't pass a large number of scanlines at once if
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2802 you want fine resolution in the progress count. (If you really need to use
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2803 the callback mechanism for time-critical tasks like mouse tracking, you could
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2804 insert additional calls inside some of the library's inner loops.)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2805
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2806 To establish a progress-monitor callback, create a struct jpeg_progress_mgr,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2807 fill in its progress_monitor field with a pointer to your callback routine,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2808 and set cinfo->progress to point to the struct. The callback will be called
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2809 whenever cinfo->progress is non-NULL. (This pointer is set to NULL by
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2810 jpeg_create_compress or jpeg_create_decompress; the library will not change
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2811 it thereafter. So if you allocate dynamic storage for the progress struct,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2812 make sure it will live as long as the JPEG object does. Allocating from the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2813 JPEG memory manager with lifetime JPOOL_PERMANENT will work nicely.) You
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2814 can use the same callback routine for both compression and decompression.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2815
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2816 The jpeg_progress_mgr struct contains four fields which are set by the library:
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2817 long pass_counter; /* work units completed in this pass */
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2818 long pass_limit; /* total number of work units in this pass */
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2819 int completed_passes; /* passes completed so far */
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2820 int total_passes; /* total number of passes expected */
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2821 During any one pass, pass_counter increases from 0 up to (not including)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2822 pass_limit; the step size is usually but not necessarily 1. The pass_limit
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2823 value may change from one pass to another. The expected total number of
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2824 passes is in total_passes, and the number of passes already completed is in
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2825 completed_passes. Thus the fraction of work completed may be estimated as
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2826 completed_passes + (pass_counter/pass_limit)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2827 --------------------------------------------
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2828 total_passes
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2829 ignoring the fact that the passes may not be equal amounts of work.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2830
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2831 When decompressing, pass_limit can even change within a pass, because it
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2832 depends on the number of scans in the JPEG file, which isn't always known in
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2833 advance. The computed fraction-of-work-done may jump suddenly (if the library
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2834 discovers it has overestimated the number of scans) or even decrease (in the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2835 opposite case). It is not wise to put great faith in the work estimate.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2836
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2837 When using the decompressor's buffered-image mode, the progress monitor work
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2838 estimate is likely to be completely unhelpful, because the library has no way
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2839 to know how many output passes will be demanded of it. Currently, the library
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2840 sets total_passes based on the assumption that there will be one more output
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2841 pass if the input file end hasn't yet been read (jpeg_input_complete() isn't
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2842 TRUE), but no more output passes if the file end has been reached when the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2843 output pass is started. This means that total_passes will rise as additional
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2844 output passes are requested. If you have a way of determining the input file
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2845 size, estimating progress based on the fraction of the file that's been read
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2846 will probably be more useful than using the library's value.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2847
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2848
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2849 Memory management
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2850 -----------------
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2851
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2852 This section covers some key facts about the JPEG library's built-in memory
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2853 manager. For more info, please read structure.txt's section about the memory
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2854 manager, and consult the source code if necessary.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2855
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2856 All memory and temporary file allocation within the library is done via the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2857 memory manager. If necessary, you can replace the "back end" of the memory
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2858 manager to control allocation yourself (for example, if you don't want the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2859 library to use malloc() and free() for some reason).
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2860
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2861 Some data is allocated "permanently" and will not be freed until the JPEG
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2862 object is destroyed. Most data is allocated "per image" and is freed by
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2863 jpeg_finish_compress, jpeg_finish_decompress, or jpeg_abort. You can call the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2864 memory manager yourself to allocate structures that will automatically be
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2865 freed at these times. Typical code for this is
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2866 ptr = (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, size);
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2867 Use JPOOL_PERMANENT to get storage that lasts as long as the JPEG object.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2868 Use alloc_large instead of alloc_small for anything bigger than a few Kbytes.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2869 There are also alloc_sarray and alloc_barray routines that automatically
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2870 build 2-D sample or block arrays.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2871
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2872 The library's minimum space requirements to process an image depend on the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2873 image's width, but not on its height, because the library ordinarily works
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2874 with "strip" buffers that are as wide as the image but just a few rows high.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2875 Some operating modes (eg, two-pass color quantization) require full-image
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2876 buffers. Such buffers are treated as "virtual arrays": only the current strip
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2877 need be in memory, and the rest can be swapped out to a temporary file.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2878
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2879 If you use the simplest memory manager back end (jmemnobs.c), then no
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2880 temporary files are used; virtual arrays are simply malloc()'d. Images bigger
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2881 than memory can be processed only if your system supports virtual memory.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2882 The other memory manager back ends support temporary files of various flavors
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2883 and thus work in machines without virtual memory. They may also be useful on
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2884 Unix machines if you need to process images that exceed available swap space.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2885
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2886 When using temporary files, the library will make the in-memory buffers for
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2887 its virtual arrays just big enough to stay within a "maximum memory" setting.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2888 Your application can set this limit by setting cinfo->mem->max_memory_to_use
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2889 after creating the JPEG object. (Of course, there is still a minimum size for
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2890 the buffers, so the max-memory setting is effective only if it is bigger than
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2891 the minimum space needed.) If you allocate any large structures yourself, you
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2892 must allocate them before jpeg_start_compress() or jpeg_start_decompress() in
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2893 order to have them counted against the max memory limit. Also keep in mind
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2894 that space allocated with alloc_small() is ignored, on the assumption that
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2895 it's too small to be worth worrying about; so a reasonable safety margin
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2896 should be left when setting max_memory_to_use.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2897
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2898 If you use the jmemname.c or jmemdos.c memory manager back end, it is
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2899 important to clean up the JPEG object properly to ensure that the temporary
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2900 files get deleted. (This is especially crucial with jmemdos.c, where the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2901 "temporary files" may be extended-memory segments; if they are not freed,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2902 DOS will require a reboot to recover the memory.) Thus, with these memory
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2903 managers, it's a good idea to provide a signal handler that will trap any
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2904 early exit from your program. The handler should call either jpeg_abort()
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2905 or jpeg_destroy() for any active JPEG objects. A handler is not needed with
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2906 jmemnobs.c, and shouldn't be necessary with jmemansi.c or jmemmac.c either,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2907 since the C library is supposed to take care of deleting files made with
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2908 tmpfile().
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2909
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2910
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2911 Memory usage
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2912 ------------
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2913
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2914 Working memory requirements while performing compression or decompression
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2915 depend on image dimensions, image characteristics (such as colorspace and
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2916 JPEG process), and operating mode (application-selected options).
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2917
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2918 As of v6b, the decompressor requires:
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2919 1. About 24K in more-or-less-fixed-size data. This varies a bit depending
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2920 on operating mode and image characteristics (particularly color vs.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2921 grayscale), but it doesn't depend on image dimensions.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2922 2. Strip buffers (of size proportional to the image width) for IDCT and
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2923 upsampling results. The worst case for commonly used sampling factors
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2924 is about 34 bytes * width in pixels for a color image. A grayscale image
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2925 only needs about 8 bytes per pixel column.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2926 3. A full-image DCT coefficient buffer is needed to decode a multi-scan JPEG
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2927 file (including progressive JPEGs), or whenever you select buffered-image
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2928 mode. This takes 2 bytes/coefficient. At typical 2x2 sampling, that's
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2929 3 bytes per pixel for a color image. Worst case (1x1 sampling) requires
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2930 6 bytes/pixel. For grayscale, figure 2 bytes/pixel.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2931 4. To perform 2-pass color quantization, the decompressor also needs a
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2932 128K color lookup table and a full-image pixel buffer (3 bytes/pixel).
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2933 This does not count any memory allocated by the application, such as a
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2934 buffer to hold the final output image.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2935
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2936 The above figures are valid for 8-bit JPEG data precision and a machine with
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2937 32-bit ints. For 9-bit to 12-bit JPEG data, double the size of the strip
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2938 buffers and quantization pixel buffer. The "fixed-size" data will be
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2939 somewhat smaller with 16-bit ints, larger with 64-bit ints. Also, CMYK
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2940 or other unusual color spaces will require different amounts of space.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2941
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2942 The full-image coefficient and pixel buffers, if needed at all, do not
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2943 have to be fully RAM resident; you can have the library use temporary
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2944 files instead when the total memory usage would exceed a limit you set.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2945 (But if your OS supports virtual memory, it's probably better to just use
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2946 jmemnobs and let the OS do the swapping.)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2947
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2948 The compressor's memory requirements are similar, except that it has no need
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2949 for color quantization. Also, it needs a full-image DCT coefficient buffer
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2950 if Huffman-table optimization is asked for, even if progressive mode is not
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2951 requested.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2952
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2953 If you need more detailed information about memory usage in a particular
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2954 situation, you can enable the MEM_STATS code in jmemmgr.c.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2955
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2956
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2957 Library compile-time options
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2958 ----------------------------
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2959
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2960 A number of compile-time options are available by modifying jmorecfg.h.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2961
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2962 The IJG code currently supports 8-bit to 12-bit sample data precision by
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2963 defining BITS_IN_JSAMPLE as 8, 9, 10, 11, or 12.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2964 Note that a value larger than 8 causes JSAMPLE to be larger than a char,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2965 so it affects the surrounding application's image data.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2966 The sample applications cjpeg and djpeg can support deeper than 8-bit data
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2967 only for PPM and GIF file formats; you must disable the other file formats
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2968 to compile a 9-bit to 12-bit cjpeg or djpeg. (install.txt has more
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2969 information about that.)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2970 Run-time selection and conversion of data precision are currently not
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2971 supported and may be added later.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2972 Exception: The transcoding part (jpegtran) supports all settings in a
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2973 single instance, since it operates on the level of DCT coefficients and
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2974 not sample values.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2975 (If you need to include an 8-bit library and a 9-bit to 12-bit library for
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2976 compression or decompression in a single application, you could probably do
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2977 it by defining NEED_SHORT_EXTERNAL_NAMES for just one of the copies. You'd
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2978 have to access the 8-bit and the 9-bit to 12-bit copies from separate
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2979 application source files. This is untested ... if you try it, we'd like to
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2980 hear whether it works!)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2981
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2982 Note that the standard Huffman tables are only valid for 8-bit data precision.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2983 If you selected more than 8-bit data precision, cjpeg uses arithmetic coding
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2984 by default. The Huffman encoder normally uses entropy optimization to
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2985 compute usable tables for higher precision. Otherwise, you'll have to
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2986 supply different default Huffman tables. You may also want to supply your
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2987 own DCT quantization tables; the existing quality-scaling code has been
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2988 developed for 8-bit use, and probably doesn't generate especially good tables
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2989 for 9-bit to 12-bit.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2990
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2991 The maximum number of components (color channels) in the image is determined
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2992 by MAX_COMPONENTS. The JPEG standard allows up to 255 components, but we
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2993 expect that few applications will need more than four or so.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2994
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2995 On machines with unusual data type sizes, you may be able to improve
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2996 performance or reduce memory space by tweaking the various typedefs in
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2997 jmorecfg.h. In particular, on some RISC CPUs, access to arrays of "short"s
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2998 is quite slow; consider trading memory for speed by making JCOEF, INT16, and
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	2999 UINT16 be "int" or "unsigned int". UINT8 is also a candidate to become int.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3000 You probably don't want to make JSAMPLE be int unless you have lots of memory
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3001 to burn.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3002
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3003 You can reduce the size of the library by compiling out various optional
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3004 functions. To do this, undefine xxx_SUPPORTED symbols as necessary.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3005
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3006 You can also save a few K by not having text error messages in the library;
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3007 the standard error message table occupies about 5Kb. This is particularly
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3008 reasonable for embedded applications where there's no good way to display
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3009 a message anyway. To do this, remove the creation of the message table
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3010 (jpeg_std_message_table[]) from jerror.c, and alter format_message to do
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3011 something reasonable without it. You could output the numeric value of the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3012 message code number, for example. If you do this, you can also save a couple
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3013 more K by modifying the TRACEMSn() macros in jerror.h to expand to nothing;
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3014 you don't need trace capability anyway, right?
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3015
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3016
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3017 Portability considerations
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3018 --------------------------
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3019
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3020 The JPEG library has been written to be extremely portable; the sample
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3021 applications cjpeg and djpeg are slightly less so. This section summarizes
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3022 the design goals in this area. (If you encounter any bugs that cause the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3023 library to be less portable than is claimed here, we'd appreciate hearing
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3024 about them.)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3025
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3026 The code works fine on ANSI C, C++, and pre-ANSI C compilers, using any of
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3027 the popular system include file setups, and some not-so-popular ones too.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3028 See install.txt for configuration procedures.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3029
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3030 The code is not dependent on the exact sizes of the C data types. As
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3031 distributed, we make the assumptions that
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3032 char is at least 8 bits wide
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3033 short is at least 16 bits wide
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3034 int is at least 16 bits wide
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3035 long is at least 32 bits wide
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3036 (These are the minimum requirements of the ANSI C standard.) Wider types will
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3037 work fine, although memory may be used inefficiently if char is much larger
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3038 than 8 bits or short is much bigger than 16 bits. The code should work
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3039 equally well with 16- or 32-bit ints.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3040
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3041 In a system where these assumptions are not met, you may be able to make the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3042 code work by modifying the typedefs in jmorecfg.h. However, you will probably
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3043 have difficulty if int is less than 16 bits wide, since references to plain
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3044 int abound in the code.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3045
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3046 char can be either signed or unsigned, although the code runs faster if an
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3047 unsigned char type is available. If char is wider than 8 bits, you will need
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3048 to redefine JOCTET and/or provide custom data source/destination managers so
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3049 that JOCTET represents exactly 8 bits of data on external storage.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3050
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3051 The JPEG library proper does not assume ASCII representation of characters.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3052 But some of the image file I/O modules in cjpeg/djpeg do have ASCII
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3053 dependencies in file-header manipulation; so does cjpeg's select_file_type()
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3054 routine.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3055
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3056 The JPEG library does not rely heavily on the C library. In particular, C
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3057 stdio is used only by the data source/destination modules and the error
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3058 handler, all of which are application-replaceable. (cjpeg/djpeg are more
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3059 heavily dependent on stdio.) malloc and free are called only from the memory
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3060 manager "back end" module, so you can use a different memory allocator by
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3061 replacing that one file.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3062
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3063 The code generally assumes that C names must be unique in the first 15
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3064 characters. However, global function names can be made unique in the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3065 first 6 characters by defining NEED_SHORT_EXTERNAL_NAMES.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3066
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3067 More info about porting the code may be gleaned by reading jconfig.txt,
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3068 jmorecfg.h, and jinclude.h.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3069
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3070
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3071 Notes for MS-DOS implementors
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3072 -----------------------------
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3073
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3074 The IJG code is designed to work efficiently in 80x86 "small" or "medium"
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3075 memory models (i.e., data pointers are 16 bits unless explicitly declared
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3076 "far"; code pointers can be either size). You may be able to use small
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3077 model to compile cjpeg or djpeg by itself, but you will probably have to use
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3078 medium model for any larger application. This won't make much difference in
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3079 performance. You will take a noticeable performance hit if you use a
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3080 large-data memory model (perhaps 10%-25%), and you should avoid "huge" model
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3081 if at all possible.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3082
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3083 The JPEG library typically needs 2Kb-3Kb of stack space. It will also
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3084 malloc about 20K-30K of near heap space while executing (and lots of far
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3085 heap, but that doesn't count in this calculation). This figure will vary
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3086 depending on selected operating mode, and to a lesser extent on image size.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3087 There is also about 5Kb-6Kb of constant data which will be allocated in the
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3088 near data segment (about 4Kb of this is the error message table).
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3089 Thus you have perhaps 20K available for other modules' static data and near
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3090 heap space before you need to go to a larger memory model. The C library's
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3091 static data will account for several K of this, but that still leaves a good
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3092 deal for your needs. (If you are tight on space, you could reduce the sizes
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3093 of the I/O buffers allocated by jdatasrc.c and jdatadst.c, say from 4K to
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3094 1K. Another possibility is to move the error message table to far memory;
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3095 this should be doable with only localized hacking on jerror.c.)
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3096
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3097 About 2K of the near heap space is "permanent" memory that will not be
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3098 released until you destroy the JPEG object. This is only an issue if you
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3099 save a JPEG object between compression or decompression operations.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3100
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3101 Far data space may also be a tight resource when you are dealing with large
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3102 images. The most memory-intensive case is decompression with two-pass color
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3103 quantization, or single-pass quantization to an externally supplied color
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3104 map. This requires a 128Kb color lookup table plus strip buffers amounting
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3105 to about 40 bytes per column for typical sampling ratios (eg, about 25600
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3106 bytes for a 640-pixel-wide image). You may not be able to process wide
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3107 images if you have large data structures of your own.
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3108
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3109 Of course, all of these concerns vanish if you use a 32-bit flat-memory-model
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3110 compiler, such as DJGPP or Watcom C. We highly recommend flat model if you
b50eed0cc0ef ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. Franz Glasner <fzglas.hg@dom66.de> parents: diff changeset	3111 can use it; the JPEG library is significantly faster in flat model.

Mercurial > hgrepos > Python2 > PyMuPDF

annotate mupdf-source/thirdparty/libjpeg/libjpeg.txt @ 46:7ee69f120f19 default tip