/src/libjpeg-turbo.main/transupp.h
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1 | | /* |
2 | | * transupp.h |
3 | | * |
4 | | * This file was part of the Independent JPEG Group's software: |
5 | | * Copyright (C) 1997-2019, Thomas G. Lane, Guido Vollbeding. |
6 | | * libjpeg-turbo Modifications: |
7 | | * Copyright (C) 2017, 2021, D. R. Commander. |
8 | | * For conditions of distribution and use, see the accompanying README.ijg |
9 | | * file. |
10 | | * |
11 | | * This file contains declarations for image transformation routines and |
12 | | * other utility code used by the jpegtran sample application. These are |
13 | | * NOT part of the core JPEG library. But we keep these routines separate |
14 | | * from jpegtran.c to ease the task of maintaining jpegtran-like programs |
15 | | * that have other user interfaces. |
16 | | * |
17 | | * NOTE: all the routines declared here have very specific requirements |
18 | | * about when they are to be executed during the reading and writing of the |
19 | | * source and destination files. See the comments in transupp.c, or see |
20 | | * jpegtran.c for an example of correct usage. |
21 | | */ |
22 | | |
23 | | /* If you happen not to want the image transform support, disable it here */ |
24 | | #ifndef TRANSFORMS_SUPPORTED |
25 | | #define TRANSFORMS_SUPPORTED 1 /* 0 disables transform code */ |
26 | | #endif |
27 | | |
28 | | /* |
29 | | * Although rotating and flipping data expressed as DCT coefficients is not |
30 | | * hard, there is an asymmetry in the JPEG format specification for images |
31 | | * whose dimensions aren't multiples of the iMCU size. The right and bottom |
32 | | * image edges are padded out to the next iMCU boundary with junk data; but |
33 | | * no padding is possible at the top and left edges. If we were to flip |
34 | | * the whole image including the pad data, then pad garbage would become |
35 | | * visible at the top and/or left, and real pixels would disappear into the |
36 | | * pad margins --- perhaps permanently, since encoders & decoders may not |
37 | | * bother to preserve DCT blocks that appear to be completely outside the |
38 | | * nominal image area. So, we have to exclude any partial iMCUs from the |
39 | | * basic transformation. |
40 | | * |
41 | | * Transpose is the only transformation that can handle partial iMCUs at the |
42 | | * right and bottom edges completely cleanly. flip_h can flip partial iMCUs |
43 | | * at the bottom, but leaves any partial iMCUs at the right edge untouched. |
44 | | * Similarly flip_v leaves any partial iMCUs at the bottom edge untouched. |
45 | | * The other transforms are defined as combinations of these basic transforms |
46 | | * and process edge blocks in a way that preserves the equivalence. |
47 | | * |
48 | | * The "trim" option causes untransformable partial iMCUs to be dropped; |
49 | | * this is not strictly lossless, but it usually gives the best-looking |
50 | | * result for odd-size images. Note that when this option is active, |
51 | | * the expected mathematical equivalences between the transforms may not hold. |
52 | | * (For example, -rot 270 -trim trims only the bottom edge, but -rot 90 -trim |
53 | | * followed by -rot 180 -trim trims both edges.) |
54 | | * |
55 | | * We also offer a lossless-crop option, which discards data outside a given |
56 | | * image region but losslessly preserves what is inside. Like the rotate and |
57 | | * flip transforms, lossless crop is restricted by the JPEG format: the upper |
58 | | * left corner of the selected region must fall on an iMCU boundary. If this |
59 | | * does not hold for the given crop parameters, we silently move the upper left |
60 | | * corner up and/or left to make it so, simultaneously increasing the region |
61 | | * dimensions to keep the lower right crop corner unchanged. (Thus, the |
62 | | * output image covers at least the requested region, but may cover more.) |
63 | | * The adjustment of the region dimensions may be optionally disabled. |
64 | | * |
65 | | * A complementary lossless wipe option is provided to discard (gray out) data |
66 | | * inside a given image region while losslessly preserving what is outside. |
67 | | * A lossless drop option is also provided, which allows another JPEG image to |
68 | | * be inserted ("dropped") into the source image data at a given position, |
69 | | * replacing the existing image data at that position. Both the source image |
70 | | * and the drop image must have the same subsampling level. It is best if they |
71 | | * also have the same quantization (quality.) Otherwise, the quantization of |
72 | | * the output image will be adapted to accommodate the higher of the source |
73 | | * image quality and the drop image quality. The trim option can be used with |
74 | | * the drop option to requantize the drop image to match the source image. |
75 | | * |
76 | | * We also provide a lossless-resize option, which is kind of a lossless-crop |
77 | | * operation in the DCT coefficient block domain - it discards higher-order |
78 | | * coefficients and losslessly preserves lower-order coefficients of a |
79 | | * sub-block. |
80 | | * |
81 | | * Rotate/flip transform, resize, and crop can be requested together in a |
82 | | * single invocation. The crop is applied last --- that is, the crop region |
83 | | * is specified in terms of the destination image after transform/resize. |
84 | | * |
85 | | * We also offer a "force to grayscale" option, which simply discards the |
86 | | * chrominance channels of a YCbCr image. This is lossless in the sense that |
87 | | * the luminance channel is preserved exactly. It's not the same kind of |
88 | | * thing as the rotate/flip transformations, but it's convenient to handle it |
89 | | * as part of this package, mainly because the transformation routines have to |
90 | | * be aware of the option to know how many components to work on. |
91 | | */ |
92 | | |
93 | | |
94 | | /* |
95 | | * Codes for supported types of image transformations. |
96 | | */ |
97 | | |
98 | | typedef enum { |
99 | | JXFORM_NONE, /* no transformation */ |
100 | | JXFORM_FLIP_H, /* horizontal flip */ |
101 | | JXFORM_FLIP_V, /* vertical flip */ |
102 | | JXFORM_TRANSPOSE, /* transpose across UL-to-LR axis */ |
103 | | JXFORM_TRANSVERSE, /* transpose across UR-to-LL axis */ |
104 | | JXFORM_ROT_90, /* 90-degree clockwise rotation */ |
105 | | JXFORM_ROT_180, /* 180-degree rotation */ |
106 | | JXFORM_ROT_270, /* 270-degree clockwise (or 90 ccw) */ |
107 | | JXFORM_WIPE, /* wipe */ |
108 | | JXFORM_DROP /* drop */ |
109 | | } JXFORM_CODE; |
110 | | |
111 | | /* |
112 | | * Codes for crop parameters, which can individually be unspecified, |
113 | | * positive or negative for xoffset or yoffset, |
114 | | * positive or force or reflect for width or height. |
115 | | */ |
116 | | |
117 | | typedef enum { |
118 | | JCROP_UNSET, |
119 | | JCROP_POS, |
120 | | JCROP_NEG, |
121 | | JCROP_FORCE, |
122 | | JCROP_REFLECT |
123 | | } JCROP_CODE; |
124 | | |
125 | | /* |
126 | | * Transform parameters struct. |
127 | | * NB: application must not change any elements of this struct after |
128 | | * calling jtransform_request_workspace. |
129 | | */ |
130 | | |
131 | | typedef struct { |
132 | | /* Options: set by caller */ |
133 | | JXFORM_CODE transform; /* image transform operator */ |
134 | | boolean perfect; /* if TRUE, fail if partial MCUs are requested */ |
135 | | boolean trim; /* if TRUE, trim partial MCUs as needed */ |
136 | | boolean force_grayscale; /* if TRUE, convert color image to grayscale */ |
137 | | boolean crop; /* if TRUE, crop or wipe source image, or drop */ |
138 | | boolean slow_hflip; /* For best performance, the JXFORM_FLIP_H transform |
139 | | normally modifies the source coefficients in place. |
140 | | Setting this to TRUE will instead use a slower, |
141 | | double-buffered algorithm, which leaves the source |
142 | | coefficients in tact (necessary if other transformed |
143 | | images must be generated from the same set of |
144 | | coefficients. */ |
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(jpeg_transform_info *info, |
180 | | const char *spec); |
181 | | /* Request any required workspace */ |
182 | | EXTERN(boolean) jtransform_request_workspace(j_decompress_ptr srcinfo, |
183 | | jpeg_transform_info *info); |
184 | | /* Adjust output image parameters */ |
185 | | EXTERN(jvirt_barray_ptr *) jtransform_adjust_parameters |
186 | | (j_decompress_ptr srcinfo, j_compress_ptr dstinfo, |
187 | | jvirt_barray_ptr *src_coef_arrays, jpeg_transform_info *info); |
188 | | /* Execute the actual transformation, if any */ |
189 | | EXTERN(void) jtransform_execute_transform(j_decompress_ptr srcinfo, |
190 | | j_compress_ptr dstinfo, |
191 | | jvirt_barray_ptr *src_coef_arrays, |
192 | | jpeg_transform_info *info); |
193 | | /* Determine whether lossless transformation is perfectly |
194 | | * possible for a specified image and transformation. |
195 | | */ |
196 | | EXTERN(boolean) jtransform_perfect_transform(JDIMENSION image_width, |
197 | | JDIMENSION image_height, |
198 | | int MCU_width, int MCU_height, |
199 | | JXFORM_CODE transform); |
200 | | |
201 | | /* jtransform_execute_transform used to be called |
202 | | * jtransform_execute_transformation, but some compilers complain about |
203 | | * routine names that long. This macro is here to avoid breaking any |
204 | | * old source code that uses the original name... |
205 | | */ |
206 | 0 | #define jtransform_execute_transformation jtransform_execute_transform |
207 | | |
208 | | #endif /* TRANSFORMS_SUPPORTED */ |
209 | | |
210 | | |
211 | | /* |
212 | | * Support for copying optional markers from source to destination file. |
213 | | */ |
214 | | |
215 | | typedef enum { |
216 | | JCOPYOPT_NONE, /* copy no optional markers */ |
217 | | JCOPYOPT_COMMENTS, /* copy only comment (COM) markers */ |
218 | | JCOPYOPT_ALL, /* copy all optional markers */ |
219 | | JCOPYOPT_ALL_EXCEPT_ICC, /* copy all optional markers except APP2 */ |
220 | | JCOPYOPT_ICC /* copy only ICC profile (APP2) markers */ |
221 | | } JCOPY_OPTION; |
222 | | |
223 | | #define JCOPYOPT_DEFAULT JCOPYOPT_COMMENTS /* recommended default */ |
224 | | |
225 | | /* Setup decompression object to save desired markers in memory */ |
226 | | EXTERN(void) jcopy_markers_setup(j_decompress_ptr srcinfo, |
227 | | JCOPY_OPTION option); |
228 | | /* Copy markers saved in the given source object to the destination object */ |
229 | | EXTERN(void) jcopy_markers_execute(j_decompress_ptr srcinfo, |
230 | | j_compress_ptr dstinfo, |
231 | | JCOPY_OPTION option); |