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transupp.h
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1 /*
2  * transupp.h
3  *
4  * Copyright (C) 1997-2011, 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 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  * The adjustment of the region dimensions may be optionally disabled.
61  *
62  * We also provide a lossless-resize option, which is kind of a lossless-crop
63  * operation in the DCT coefficient block domain - it discards higher-order
64  * coefficients and losslessly preserves lower-order coefficients of a
65  * sub-block.
66  *
67  * Rotate/flip transform, resize, and crop can be requested together in a
68  * single invocation. The crop is applied last --- that is, the crop region
69  * is specified in terms of the destination image after transform/resize.
70  *
71  * We also offer a "force to grayscale" option, which simply discards the
72  * chrominance channels of a YCbCr image. This is lossless in the sense that
73  * the luminance channel is preserved exactly. It's not the same kind of
74  * thing as the rotate/flip transformations, but it's convenient to handle it
75  * as part of this package, mainly because the transformation routines have to
76  * be aware of the option to know how many components to work on.
77  */
78 
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  * Codes for supported types of image transformations.
93  */
94 
95 typedef enum {
96  JXFORM_NONE, /* no transformation */
97  JXFORM_FLIP_H, /* horizontal flip */
98  JXFORM_FLIP_V, /* vertical flip */
99  JXFORM_TRANSPOSE, /* transpose across UL-to-LR axis */
100  JXFORM_TRANSVERSE, /* transpose across UR-to-LL axis */
101  JXFORM_ROT_90, /* 90-degree clockwise rotation */
102  JXFORM_ROT_180, /* 180-degree rotation */
103  JXFORM_ROT_270 /* 270-degree clockwise (or 90 ccw) */
104 } JXFORM_CODE;
105 
106 /*
107  * Codes for crop parameters, which can individually be unspecified,
108  * positive or negative for xoffset or yoffset,
109  * positive or forced for width or height.
110  */
111 
112 typedef enum {
117 } JCROP_CODE;
118 
119 /*
120  * Transform parameters struct.
121  * NB: application must not change any elements of this struct after
122  * calling jtransform_request_workspace.
123  */
124 
125 typedef struct {
126  /* Options: set by caller */
127  JXFORM_CODE transform; /* image transform operator */
128  boolean perfect; /* if TRUE, fail if partial MCUs are requested */
129  boolean trim; /* if TRUE, trim partial MCUs as needed */
130  boolean force_grayscale; /* if TRUE, convert color image to grayscale */
131  boolean crop; /* if TRUE, crop source image */
132  boolean slow_hflip; /* For best performance, the JXFORM_FLIP_H transform
133  normally modifies the source coefficients in place.
134  Setting this to TRUE will instead use a slower,
135  double-buffered algorithm, which leaves the source
136  coefficients intact (necessary if other transformed
137  images must be generated from the same set of
138  coefficients. */
139 
140  /* Crop parameters: application need not set these unless crop is TRUE.
141  * These can be filled in by jtransform_parse_crop_spec().
142  */
143  JDIMENSION crop_width; /* Width of selected region */
144  JCROP_CODE crop_width_set; /* (forced disables adjustment) */
145  JDIMENSION crop_height; /* Height of selected region */
146  JCROP_CODE crop_height_set; /* (forced disables adjustment) */
147  JDIMENSION crop_xoffset; /* X offset of selected region */
148  JCROP_CODE crop_xoffset_set; /* (negative measures from right edge) */
149  JDIMENSION crop_yoffset; /* Y offset of selected region */
150  JCROP_CODE crop_yoffset_set; /* (negative measures from bottom edge) */
151 
152  /* Internal workspace: caller should not touch these */
153  int num_components; /* # of components in workspace */
154  jvirt_barray_ptr * workspace_coef_arrays; /* workspace for transformations */
155  JDIMENSION output_width; /* cropped destination dimensions */
156  JDIMENSION output_height;
157  JDIMENSION x_crop_offset; /* destination crop offsets measured in iMCUs */
158  JDIMENSION y_crop_offset;
159  int iMCU_sample_width; /* destination iMCU size */
162 
163 #if TRANSFORMS_SUPPORTED
164 
165 /* Request any required workspace */
166 EXTERN(boolean) jtransform_request_workspace
167  (j_decompress_ptr srcinfo, jpeg_transform_info *info);
168 /* Adjust output image parameters */
169 EXTERN(jvirt_barray_ptr *) jtransform_adjust_parameters
170  (j_decompress_ptr srcinfo, j_compress_ptr dstinfo,
171  jvirt_barray_ptr *src_coef_arrays,
172  jpeg_transform_info *info);
173 /* Execute the actual transformation, if any */
174 EXTERN(void) jtransform_execute_transform
175  (j_decompress_ptr srcinfo, j_compress_ptr dstinfo,
176  jvirt_barray_ptr *src_coef_arrays,
177  jpeg_transform_info *info);
178 /* Determine whether lossless transformation is perfectly
179  * possible for a specified image and transformation.
180  */
181 EXTERN(boolean) jtransform_perfect_transform
182  (JDIMENSION image_width, JDIMENSION image_height,
183  int MCU_width, int MCU_height,
184  JXFORM_CODE transform);
185 
186 /* jtransform_execute_transform used to be called
187  * jtransform_execute_transformation, but some compilers complain about
188  * routine names that long. This macro is here to avoid breaking any
189  * old source code that uses the original name...
190  */
191 #define jtransform_execute_transformation jtransform_execute_transform
192 
193 #endif /* TRANSFORMS_SUPPORTED */
194 
195 /*
196  * Support for copying optional markers from source to destination file.
197  */
198 
199 typedef enum {
200  JCOPYOPT_NONE, /* copy no optional markers */
201  JCOPYOPT_COMMENTS, /* copy only comment (COM) markers */
202  JCOPYOPT_ALL /* copy all optional markers */
203 } JCOPY_OPTION;
204 
205 
206 /* Setup decompression object to save desired markers in memory */
208  (j_decompress_ptr srcinfo, JCOPY_OPTION option);
209 /* Copy markers saved in the given source object to the destination object */
211  (j_decompress_ptr srcinfo, j_compress_ptr dstinfo,
212  JCOPY_OPTION option);
JDIMENSION crop_height
Definition: transupp.h:145
JCROP_CODE crop_height_set
Definition: transupp.h:146
JDIMENSION crop_yoffset
Definition: transupp.h:149
JDIMENSION crop_xoffset
Definition: transupp.h:147
JCOPY_OPTION option
Definition: transupp.h:208
j_compress_ptr dstinfo
Definition: transupp.h:211
JDIMENSION output_height
Definition: transupp.h:156
jcopy_markers_execute(j_decompress_ptr srcinfo, j_compress_ptr dstinfo, JCOPY_OPTION option)
Definition: transupp.c:1526
boolean force_grayscale
Definition: transupp.h:130
JXFORM_CODE transform
Definition: transupp.h:127
JDIMENSION x_crop_offset
Definition: transupp.h:157
EXTERN(void) jcopy_markers_setup(j_decompress_ptr srcinfo
JDIMENSION crop_width
Definition: transupp.h:143
JDIMENSION y_crop_offset
Definition: transupp.h:158
JCROP_CODE crop_xoffset_set
Definition: transupp.h:148
JXFORM_CODE
Definition: transupp.h:95
jcopy_markers_setup(j_decompress_ptr srcinfo, JCOPY_OPTION option)
Definition: transupp.c:1499
JDIMENSION output_width
Definition: transupp.h:155
boolean slow_hflip
Definition: transupp.h:132
JCROP_CODE
Definition: transupp.h:112
jvirt_barray_ptr * workspace_coef_arrays
Definition: transupp.h:154
JCROP_CODE crop_yoffset_set
Definition: transupp.h:150
JCROP_CODE crop_width_set
Definition: transupp.h:144
JCOPY_OPTION
Definition: transupp.h:199