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comparison mupdf-source/thirdparty/libjpeg/jdtrans.c @ 2:b50eed0cc0ef upstream

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ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. The directory name has changed: no version number in the expanded directory now.
author Franz Glasner <fzglas.hg@dom66.de>
date Mon, 15 Sep 2025 11:43:07 +0200
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1:1d09e1dec1d9 2:b50eed0cc0ef
1 /*
2 * jdtrans.c
3 *
4 * Copyright (C) 1995-1997, Thomas G. Lane.
5 * Modified 2000-2009 by Guido Vollbeding.
6 * This file is part of the Independent JPEG Group's software.
7 * For conditions of distribution and use, see the accompanying README file.
8 *
9 * This file contains library routines for transcoding decompression,
10 * that is, reading raw DCT coefficient arrays from an input JPEG file.
11 * The routines in jdapimin.c will also be needed by a transcoder.
12 */
13
14 #define JPEG_INTERNALS
15 #include "jinclude.h"
16 #include "jpeglib.h"
17
18
19 /* Forward declarations */
20 LOCAL(void) transdecode_master_selection JPP((j_decompress_ptr cinfo));
21
22
23 /*
24 * Read the coefficient arrays from a JPEG file.
25 * jpeg_read_header must be completed before calling this.
26 *
27 * The entire image is read into a set of virtual coefficient-block arrays,
28 * one per component. The return value is a pointer to the array of
29 * virtual-array descriptors. These can be manipulated directly via the
30 * JPEG memory manager, or handed off to jpeg_write_coefficients().
31 * To release the memory occupied by the virtual arrays, call
32 * jpeg_finish_decompress() when done with the data.
33 *
34 * An alternative usage is to simply obtain access to the coefficient arrays
35 * during a buffered-image-mode decompression operation. This is allowed
36 * after any jpeg_finish_output() call. The arrays can be accessed until
37 * jpeg_finish_decompress() is called. (Note that any call to the library
38 * may reposition the arrays, so don't rely on access_virt_barray() results
39 * to stay valid across library calls.)
40 *
41 * Returns NULL if suspended. This case need be checked only if
42 * a suspending data source is used.
43 */
44
45 GLOBAL(jvirt_barray_ptr *)
46 jpeg_read_coefficients (j_decompress_ptr cinfo)
47 {
48 if (cinfo->global_state == DSTATE_READY) {
49 /* First call: initialize active modules */
50 transdecode_master_selection(cinfo);
51 cinfo->global_state = DSTATE_RDCOEFS;
52 }
53 if (cinfo->global_state == DSTATE_RDCOEFS) {
54 /* Absorb whole file into the coef buffer */
55 for (;;) {
56 int retcode;
57 /* Call progress monitor hook if present */
58 if (cinfo->progress != NULL)
59 (*cinfo->progress->progress_monitor) ((j_common_ptr) cinfo);
60 /* Absorb some more input */
61 retcode = (*cinfo->inputctl->consume_input) (cinfo);
62 if (retcode == JPEG_SUSPENDED)
63 return NULL;
64 if (retcode == JPEG_REACHED_EOI)
65 break;
66 /* Advance progress counter if appropriate */
67 if (cinfo->progress != NULL &&
68 (retcode == JPEG_ROW_COMPLETED || retcode == JPEG_REACHED_SOS)) {
69 if (++cinfo->progress->pass_counter >= cinfo->progress->pass_limit) {
70 /* startup underestimated number of scans; ratchet up one scan */
71 cinfo->progress->pass_limit += (long) cinfo->total_iMCU_rows;
72 }
73 }
74 }
75 /* Set state so that jpeg_finish_decompress does the right thing */
76 cinfo->global_state = DSTATE_STOPPING;
77 }
78 /* At this point we should be in state DSTATE_STOPPING if being used
79 * standalone, or in state DSTATE_BUFIMAGE if being invoked to get access
80 * to the coefficients during a full buffered-image-mode decompression.
81 */
82 if ((cinfo->global_state == DSTATE_STOPPING ||
83 cinfo->global_state == DSTATE_BUFIMAGE) && cinfo->buffered_image) {
84 return cinfo->coef->coef_arrays;
85 }
86 /* Oops, improper usage */
87 ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
88 return NULL; /* keep compiler happy */
89 }
90
91
92 /*
93 * Master selection of decompression modules for transcoding.
94 * This substitutes for jdmaster.c's initialization of the full decompressor.
95 */
96
97 LOCAL(void)
98 transdecode_master_selection (j_decompress_ptr cinfo)
99 {
100 /* This is effectively a buffered-image operation. */
101 cinfo->buffered_image = TRUE;
102
103 /* Compute output image dimensions and related values. */
104 jpeg_core_output_dimensions(cinfo);
105
106 /* Entropy decoding: either Huffman or arithmetic coding. */
107 if (cinfo->arith_code)
108 jinit_arith_decoder(cinfo);
109 else {
110 jinit_huff_decoder(cinfo);
111 }
112
113 /* Always get a full-image coefficient buffer. */
114 jinit_d_coef_controller(cinfo, TRUE);
115
116 /* We can now tell the memory manager to allocate virtual arrays. */
117 (*cinfo->mem->realize_virt_arrays) ((j_common_ptr) cinfo);
118
119 /* Initialize input side of decompressor to consume first scan. */
120 (*cinfo->inputctl->start_input_pass) (cinfo);
121
122 /* Initialize progress monitoring. */
123 if (cinfo->progress != NULL) {
124 int nscans;
125 /* Estimate number of scans to set pass_limit. */
126 if (cinfo->progressive_mode) {
127 /* Arbitrarily estimate 2 interleaved DC scans + 3 AC scans/component. */
128 nscans = 2 + 3 * cinfo->num_components;
129 } else if (cinfo->inputctl->has_multiple_scans) {
130 /* For a nonprogressive multiscan file, estimate 1 scan per component. */
131 nscans = cinfo->num_components;
132 } else {
133 nscans = 1;
134 }
135 cinfo->progress->pass_counter = 0L;
136 cinfo->progress->pass_limit = (long) cinfo->total_iMCU_rows * nscans;
137 cinfo->progress->completed_passes = 0;
138 cinfo->progress->total_passes = 1;
139 }
140 }