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comparison mupdf-source/thirdparty/libjpeg/transupp.h @ 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 /*
2 * transupp.h
3 *
4 * Copyright (C) 1997-2019, Thomas G. Lane, Guido Vollbeding.
5 * This file is part of the Independent JPEG Group's software.
6 * For conditions of distribution and use, see the accompanying README file.
7 *
8 * This file contains declarations for image transformation routines and
9 * other utility code used by the jpegtran sample application. These are
10 * NOT part of the core JPEG library. But we keep these routines separate
11 * from jpegtran.c to ease the task of maintaining jpegtran-like programs
12 * that have other user interfaces.
13 *
14 * NOTE: all the routines declared here have very specific requirements
15 * about when they are to be executed during the reading and writing of the
16 * source and destination files. See the comments in transupp.c, or see
17 * jpegtran.c for an example of correct usage.
18 */
19
20 /* If you happen not to want the image transform support, disable it here */
21 #ifndef TRANSFORMS_SUPPORTED
22 #define TRANSFORMS_SUPPORTED 1 /* 0 disables transform code */
23 #endif
24
25 /*
26 * Although rotating and flipping data expressed as DCT coefficients is not
27 * hard, there is an asymmetry in the JPEG format specification for images
28 * whose dimensions aren't multiples of the iMCU size. The right and bottom
29 * image edges are padded out to the next iMCU boundary with junk data; but
30 * no padding is possible at the top and left edges. If we were to flip
31 * the whole image including the pad data, then pad garbage would become
32 * visible at the top and/or left, and real pixels would disappear into the
33 * pad margins --- perhaps permanently, since encoders & decoders may not
34 * bother to preserve DCT blocks that appear to be completely outside the
35 * nominal image area. So, we have to exclude any partial iMCUs from the
36 * basic transformation.
37 *
38 * Transpose is the only transformation that can handle partial iMCUs at the
39 * right and bottom edges completely cleanly. flip_h can flip partial iMCUs
40 * at the bottom, but leaves any partial iMCUs at the right edge untouched.
41 * Similarly flip_v leaves any partial iMCUs at the bottom edge untouched.
42 * The other transforms are defined as combinations of these basic transforms
43 * and process edge blocks in a way that preserves the equivalence.
44 *
45 * The "trim" option causes untransformable partial iMCUs to be dropped;
46 * this is not strictly lossless, but it usually gives the best-looking
47 * result for odd-size images. Note that when this option is active,
48 * the expected mathematical equivalences between the transforms may not hold.
49 * (For example, -rot 270 -trim trims only the bottom edge, but -rot 90 -trim
50 * followed by -rot 180 -trim trims both edges.)
51 *
52 * We also offer a lossless-crop option, which discards data outside a given
53 * image region but losslessly preserves what is inside. Like the rotate and
54 * flip transforms, lossless crop is restricted by the current JPEG format: the
55 * upper left corner of the selected region must fall on an iMCU boundary. If
56 * this does not hold for the given crop parameters, we silently move the upper
57 * left corner up and/or left to make it so, simultaneously increasing the
58 * region dimensions to keep the lower right crop corner unchanged. (Thus, the
59 * output image covers at least the requested region, but may cover more.)
60 * The adjustment of the region dimensions may be optionally disabled.
61 *
62 * A complementary lossless-wipe option is provided to discard (gray out) data
63 * inside a given image region while losslessly preserving what is outside.
64 * Another option is lossless-drop, which replaces data at a given image
65 * position by another image. Both source images must have the same
66 * subsampling values. It is best if they also have the same quantization,
67 * otherwise quantization adaption occurs. The trim option can be used with
68 * the drop option to requantize the drop file to the source file.
69 *
70 * We also provide a lossless-resize option, which is kind of a lossless-crop
71 * operation in the DCT coefficient block domain - it discards higher-order
72 * coefficients and losslessly preserves lower-order coefficients of a
73 * sub-block.
74 *
75 * Rotate/flip transform, resize, and crop can be requested together in a
76 * single invocation. The crop is applied last --- that is, the crop region
77 * is specified in terms of the destination image after transform/resize.
78 *
79 * We also offer a "force to grayscale" option, which simply discards the
80 * chrominance channels of a YCbCr image. This is lossless in the sense that
81 * the luminance channel is preserved exactly. It's not the same kind of
82 * thing as the rotate/flip transformations, but it's convenient to handle it
83 * as part of this package, mainly because the transformation routines have to
84 * be aware of the option to know how many components to work on.
85 */
86
87
88 /* Short forms of external names for systems with brain-damaged linkers. */
89
90 #ifdef NEED_SHORT_EXTERNAL_NAMES
91 #define jtransform_parse_crop_spec jTrParCrop
92 #define jtransform_request_workspace jTrRequest
93 #define jtransform_adjust_parameters jTrAdjust
94 #define jtransform_execute_transform jTrExec
95 #define jtransform_perfect_transform jTrPerfect
96 #define jcopy_markers_setup jCMrkSetup
97 #define jcopy_markers_execute jCMrkExec
98 #endif /* NEED_SHORT_EXTERNAL_NAMES */
99
100
101 /*
102 * Codes for supported types of image transformations.
103 */
104
105 typedef enum {
106 JXFORM_NONE, /* no transformation */
107 JXFORM_FLIP_H, /* horizontal flip */
108 JXFORM_FLIP_V, /* vertical flip */
109 JXFORM_TRANSPOSE, /* transpose across UL-to-LR axis */
110 JXFORM_TRANSVERSE, /* transpose across UR-to-LL axis */
111 JXFORM_ROT_90, /* 90-degree clockwise rotation */
112 JXFORM_ROT_180, /* 180-degree rotation */
113 JXFORM_ROT_270, /* 270-degree clockwise (or 90 ccw) */
114 JXFORM_WIPE, /* wipe */
115 JXFORM_DROP /* drop */
116 } JXFORM_CODE;
117
118 /*
119 * Codes for crop parameters, which can individually be unspecified,
120 * positive or negative for xoffset or yoffset,
121 * positive or force or reflect for width or height.
122 */
123
124 typedef enum {
125 JCROP_UNSET,
126 JCROP_POS,
127 JCROP_NEG,
128 JCROP_FORCE,
129 JCROP_REFLECT
130 } JCROP_CODE;
131
132 /*
133 * Transform parameters struct.
134 * NB: application must not change any elements of this struct after
135 * calling jtransform_request_workspace.
136 */
137
138 typedef struct {
139 /* Options: set by caller */
140 JXFORM_CODE transform; /* image transform operator */
141 boolean perfect; /* if TRUE, fail if partial MCUs are requested */
142 boolean trim; /* if TRUE, trim partial MCUs as needed */
143 boolean force_grayscale; /* if TRUE, convert color image to grayscale */
144 boolean crop; /* if TRUE, crop or wipe source image, or drop */
145
146 /* Crop parameters: application need not set these unless crop is TRUE.
147 * These can be filled in by jtransform_parse_crop_spec().
148 */
149 JDIMENSION crop_width; /* Width of selected region */
150 JCROP_CODE crop_width_set; /* (force disables adjustment) */
151 JDIMENSION crop_height; /* Height of selected region */
152 JCROP_CODE crop_height_set; /* (force disables adjustment) */
153 JDIMENSION crop_xoffset; /* X offset of selected region */
154 JCROP_CODE crop_xoffset_set; /* (negative measures from right edge) */
155 JDIMENSION crop_yoffset; /* Y offset of selected region */
156 JCROP_CODE crop_yoffset_set; /* (negative measures from bottom edge) */
157
158 /* Drop parameters: set by caller for drop request */
159 j_decompress_ptr drop_ptr;
160 jvirt_barray_ptr * drop_coef_arrays;
161
162 /* Internal workspace: caller should not touch these */
163 int num_components; /* # of components in workspace */
164 jvirt_barray_ptr * workspace_coef_arrays; /* workspace for transformations */
165 JDIMENSION output_width; /* cropped destination dimensions */
166 JDIMENSION output_height;
167 JDIMENSION x_crop_offset; /* destination crop offsets measured in iMCUs */
168 JDIMENSION y_crop_offset;
169 JDIMENSION drop_width; /* drop/wipe dimensions measured in iMCUs */
170 JDIMENSION drop_height;
171 int iMCU_sample_width; /* destination iMCU size */
172 int iMCU_sample_height;
173 } jpeg_transform_info;
174
175
176 #if TRANSFORMS_SUPPORTED
177
178 /* Parse a crop specification (written in X11 geometry style) */
179 EXTERN(boolean) jtransform_parse_crop_spec
180 JPP((jpeg_transform_info *info, const char *spec));
181 /* Request any required workspace */
182 EXTERN(boolean) jtransform_request_workspace
183 JPP((j_decompress_ptr srcinfo, jpeg_transform_info *info));
184 /* Adjust output image parameters */
185 EXTERN(jvirt_barray_ptr *) jtransform_adjust_parameters
186 JPP((j_decompress_ptr srcinfo, j_compress_ptr dstinfo,
187 jvirt_barray_ptr *src_coef_arrays,
188 jpeg_transform_info *info));
189 /* Execute the actual transformation, if any */
190 EXTERN(void) jtransform_execute_transform
191 JPP((j_decompress_ptr srcinfo, j_compress_ptr dstinfo,
192 jvirt_barray_ptr *src_coef_arrays,
193 jpeg_transform_info *info));
194 /* Determine whether lossless transformation is perfectly
195 * possible for a specified image and transformation.
196 */
197 EXTERN(boolean) jtransform_perfect_transform
198 JPP((JDIMENSION image_width, JDIMENSION image_height,
199 int MCU_width, int MCU_height,
200 JXFORM_CODE transform));
201
202 /* jtransform_execute_transform used to be called
203 * jtransform_execute_transformation, but some compilers complain about
204 * routine names that long. This macro is here to avoid breaking any
205 * old source code that uses the original name...
206 */
207 #define jtransform_execute_transformation jtransform_execute_transform
208
209 #endif /* TRANSFORMS_SUPPORTED */
210
211
212 /*
213 * Support for copying optional markers from source to destination file.
214 */
215
216 typedef enum {
217 JCOPYOPT_NONE, /* copy no optional markers */
218 JCOPYOPT_COMMENTS, /* copy only comment (COM) markers */
219 JCOPYOPT_ALL /* copy all optional markers */
220 } JCOPY_OPTION;
221
222 #define JCOPYOPT_DEFAULT JCOPYOPT_COMMENTS /* recommended default */
223
224 /* Setup decompression object to save desired markers in memory */
225 EXTERN(void) jcopy_markers_setup
226 JPP((j_decompress_ptr srcinfo, JCOPY_OPTION option));
227 /* Copy markers saved in the given source object to the destination object */
228 EXTERN(void) jcopy_markers_execute
229 JPP((j_decompress_ptr srcinfo, j_compress_ptr dstinfo,
230 JCOPY_OPTION option));