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transupp.h
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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 {
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 */
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 */
167  JDIMENSION x_crop_offset; /* destination crop offsets measured in iMCUs */
169  JDIMENSION drop_width; /* drop/wipe dimensions measured in iMCUs */
171  int iMCU_sample_width; /* destination iMCU size */
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
184 /* Adjust output image parameters */
185 EXTERN(jvirt_barray_ptr *) jtransform_adjust_parameters
187  jvirt_barray_ptr *src_coef_arrays,
189 /* Execute the actual transformation, if any */
190 EXTERN(void) jtransform_execute_transform
192  jvirt_barray_ptr *src_coef_arrays,
194 /* Determine whether lossless transformation is perfectly
195  * possible for a specified image and transformation.
196  */
197 EXTERN(boolean) jtransform_perfect_transform
199  int MCU_width, int MCU_height,
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 */
227 /* Copy markers saved in the given source object to the destination object */
JDIMENSION drop_height
Definition: transupp.h:170
JDIMENSION crop_height
Definition: transupp.h:151
JCROP_CODE crop_height_set
Definition: transupp.h:152
JDIMENSION crop_yoffset
Definition: transupp.h:155
JDIMENSION crop_xoffset
Definition: transupp.h:153
int image_height
j_compress_ptr dstinfo
Definition: transupp.h:229
JDIMENSION output_height
Definition: transupp.h:166
jcopy_markers_execute(j_decompress_ptr srcinfo, j_compress_ptr dstinfo, JCOPY_OPTION option)
Definition: transupp.c:2392
int image_width
j_decompress_ptr drop_ptr
Definition: transupp.h:159
Definition: getopt.h:108
boolean force_grayscale
Definition: transupp.h:143
JXFORM_CODE transform
Definition: transupp.h:140
JDIMENSION x_crop_offset
Definition: transupp.h:167
jvirt_barray_ptr * drop_coef_arrays
Definition: transupp.h:160
#define JPP(arglist)
Definition: jpeglib.h:877
JDIMENSION crop_width
Definition: transupp.h:149
JDIMENSION y_crop_offset
Definition: transupp.h:168
JCROP_CODE crop_xoffset_set
Definition: transupp.h:154
JDIMENSION drop_width
Definition: transupp.h:169
JXFORM_CODE
Definition: transupp.h:105
EXTERN(void) jcopy_markers_setup JPP((j_decompress_ptr srcinfo
jcopy_markers_setup(j_decompress_ptr srcinfo, JCOPY_OPTION option)
Definition: transupp.c:2367
JDIMENSION output_width
Definition: transupp.h:165
unsigned int JDIMENSION
Definition: jmorecfg.h:229
GLuint GLenum GLenum transform
Definition: glext.h:9407
JCROP_CODE
Definition: transupp.h:124
jvirt_barray_ptr * workspace_coef_arrays
Definition: transupp.h:164
JCROP_CODE crop_yoffset_set
Definition: transupp.h:156
JCROP_CODE crop_width_set
Definition: transupp.h:150
JCOPY_OPTION
Definition: transupp.h:216