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Thomas G. Lane5ead57a1998-03-27 00:00:00 +00001/*
2 * transupp.h
3 *
Guido Vollbeding989630f2010-01-10 00:00:00 +00004 * Copyright (C) 1997-2009, Thomas G. Lane, Guido Vollbeding.
Thomas G. Lane5ead57a1998-03-27 00:00:00 +00005 * 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
Thomas G. Lane5ead57a1998-03-27 00:00:00 +000025/*
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 *
Guido Vollbeding5996a252009-06-27 00:00:00 +000052 * 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 JPEG format: the upper
55 * left corner of the selected region must fall on an iMCU boundary. If this
56 * does not hold for the given crop parameters, we silently move the upper left
57 * corner up and/or left to make it so, simultaneously increasing the region
58 * 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 *
Guido Vollbeding989630f2010-01-10 00:00:00 +000061 * We also provide a lossless-resize option, which is kind of a lossless-crop
62 * operation in the DCT coefficient block domain - it discards higher-order
63 * coefficients and losslessly preserves lower-order coefficients of a
64 * sub-block.
65 *
66 * Rotate/flip transform, resize, and crop can be requested together in a
67 * single invocation. The crop is applied last --- that is, the crop region
68 * is specified in terms of the destination image after transform/resize.
Guido Vollbeding5996a252009-06-27 00:00:00 +000069 *
Thomas G. Lane5ead57a1998-03-27 00:00:00 +000070 * We also offer a "force to grayscale" option, which simply discards the
71 * chrominance channels of a YCbCr image. This is lossless in the sense that
72 * the luminance channel is preserved exactly. It's not the same kind of
73 * thing as the rotate/flip transformations, but it's convenient to handle it
74 * as part of this package, mainly because the transformation routines have to
75 * be aware of the option to know how many components to work on.
76 */
77
Guido Vollbeding5996a252009-06-27 00:00:00 +000078
79/* Short forms of external names for systems with brain-damaged linkers. */
80
81#ifdef NEED_SHORT_EXTERNAL_NAMES
82#define jtransform_parse_crop_spec jTrParCrop
83#define jtransform_request_workspace jTrRequest
84#define jtransform_adjust_parameters jTrAdjust
85#define jtransform_execute_transform jTrExec
86#define jtransform_perfect_transform jTrPerfect
87#define jcopy_markers_setup jCMrkSetup
88#define jcopy_markers_execute jCMrkExec
89#endif /* NEED_SHORT_EXTERNAL_NAMES */
90
91
92/*
93 * Codes for supported types of image transformations.
94 */
95
96typedef enum {
97 JXFORM_NONE, /* no transformation */
98 JXFORM_FLIP_H, /* horizontal flip */
99 JXFORM_FLIP_V, /* vertical flip */
100 JXFORM_TRANSPOSE, /* transpose across UL-to-LR axis */
101 JXFORM_TRANSVERSE, /* transpose across UR-to-LL axis */
102 JXFORM_ROT_90, /* 90-degree clockwise rotation */
103 JXFORM_ROT_180, /* 180-degree rotation */
104 JXFORM_ROT_270 /* 270-degree clockwise (or 90 ccw) */
105} JXFORM_CODE;
106
107/*
108 * Codes for crop parameters, which can individually be unspecified,
109 * positive, or negative. (Negative width or height makes no sense, though.)
110 */
111
112typedef enum {
113 JCROP_UNSET,
114 JCROP_POS,
115 JCROP_NEG
116} JCROP_CODE;
117
118/*
119 * Transform parameters struct.
120 * NB: application must not change any elements of this struct after
121 * calling jtransform_request_workspace.
122 */
123
Thomas G. Lane5ead57a1998-03-27 00:00:00 +0000124typedef struct {
125 /* Options: set by caller */
126 JXFORM_CODE transform; /* image transform operator */
Guido Vollbeding5996a252009-06-27 00:00:00 +0000127 boolean perfect; /* if TRUE, fail if partial MCUs are requested */
Thomas G. Lane5ead57a1998-03-27 00:00:00 +0000128 boolean trim; /* if TRUE, trim partial MCUs as needed */
129 boolean force_grayscale; /* if TRUE, convert color image to grayscale */
Guido Vollbeding5996a252009-06-27 00:00:00 +0000130 boolean crop; /* if TRUE, crop source image */
131
132 /* Crop parameters: application need not set these unless crop is TRUE.
133 * These can be filled in by jtransform_parse_crop_spec().
134 */
135 JDIMENSION crop_width; /* Width of selected region */
136 JCROP_CODE crop_width_set;
137 JDIMENSION crop_height; /* Height of selected region */
138 JCROP_CODE crop_height_set;
139 JDIMENSION crop_xoffset; /* X offset of selected region */
140 JCROP_CODE crop_xoffset_set; /* (negative measures from right edge) */
141 JDIMENSION crop_yoffset; /* Y offset of selected region */
142 JCROP_CODE crop_yoffset_set; /* (negative measures from bottom edge) */
Thomas G. Lane5ead57a1998-03-27 00:00:00 +0000143
144 /* Internal workspace: caller should not touch these */
145 int num_components; /* # of components in workspace */
146 jvirt_barray_ptr * workspace_coef_arrays; /* workspace for transformations */
Guido Vollbeding5996a252009-06-27 00:00:00 +0000147 JDIMENSION output_width; /* cropped destination dimensions */
148 JDIMENSION output_height;
149 JDIMENSION x_crop_offset; /* destination crop offsets measured in iMCUs */
150 JDIMENSION y_crop_offset;
Guido Vollbeding989630f2010-01-10 00:00:00 +0000151 int iMCU_sample_width; /* destination iMCU size */
152 int iMCU_sample_height;
Thomas G. Lane5ead57a1998-03-27 00:00:00 +0000153} jpeg_transform_info;
154
155
156#if TRANSFORMS_SUPPORTED
157
Guido Vollbeding5996a252009-06-27 00:00:00 +0000158/* Parse a crop specification (written in X11 geometry style) */
159EXTERN(boolean) jtransform_parse_crop_spec
160 JPP((jpeg_transform_info *info, const char *spec));
Thomas G. Lane5ead57a1998-03-27 00:00:00 +0000161/* Request any required workspace */
Guido Vollbeding989630f2010-01-10 00:00:00 +0000162EXTERN(boolean) jtransform_request_workspace
Thomas G. Lane5ead57a1998-03-27 00:00:00 +0000163 JPP((j_decompress_ptr srcinfo, jpeg_transform_info *info));
164/* Adjust output image parameters */
165EXTERN(jvirt_barray_ptr *) jtransform_adjust_parameters
166 JPP((j_decompress_ptr srcinfo, j_compress_ptr dstinfo,
167 jvirt_barray_ptr *src_coef_arrays,
168 jpeg_transform_info *info));
169/* Execute the actual transformation, if any */
Guido Vollbeding5996a252009-06-27 00:00:00 +0000170EXTERN(void) jtransform_execute_transform
Thomas G. Lane5ead57a1998-03-27 00:00:00 +0000171 JPP((j_decompress_ptr srcinfo, j_compress_ptr dstinfo,
172 jvirt_barray_ptr *src_coef_arrays,
173 jpeg_transform_info *info));
Guido Vollbeding5996a252009-06-27 00:00:00 +0000174/* Determine whether lossless transformation is perfectly
175 * possible for a specified image and transformation.
176 */
177EXTERN(boolean) jtransform_perfect_transform
178 JPP((JDIMENSION image_width, JDIMENSION image_height,
179 int MCU_width, int MCU_height,
180 JXFORM_CODE transform));
181
182/* jtransform_execute_transform used to be called
183 * jtransform_execute_transformation, but some compilers complain about
184 * routine names that long. This macro is here to avoid breaking any
185 * old source code that uses the original name...
186 */
187#define jtransform_execute_transformation jtransform_execute_transform
Thomas G. Lane5ead57a1998-03-27 00:00:00 +0000188
189#endif /* TRANSFORMS_SUPPORTED */
190
191
192/*
193 * Support for copying optional markers from source to destination file.
194 */
195
196typedef enum {
197 JCOPYOPT_NONE, /* copy no optional markers */
198 JCOPYOPT_COMMENTS, /* copy only comment (COM) markers */
199 JCOPYOPT_ALL /* copy all optional markers */
200} JCOPY_OPTION;
201
202#define JCOPYOPT_DEFAULT JCOPYOPT_COMMENTS /* recommended default */
203
204/* Setup decompression object to save desired markers in memory */
205EXTERN(void) jcopy_markers_setup
206 JPP((j_decompress_ptr srcinfo, JCOPY_OPTION option));
207/* Copy markers saved in the given source object to the destination object */
208EXTERN(void) jcopy_markers_execute
209 JPP((j_decompress_ptr srcinfo, j_compress_ptr dstinfo,
210 JCOPY_OPTION option));