source: trunk/libjpeg/transupp.h @ 283

Last change on this file since 283 was 283, checked in by rbri, 12 years ago

JPEG plugin: libjpeg updated to version 7

File size: 8.7 KB
Line 
1/*
2 * transupp.h
3 *
4 * Copyright (C) 1997-2001, Thomas G. Lane.
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 *
61 * If both crop and a rotate/flip transform are requested, the crop is applied
62 * last --- that is, the crop region is specified in terms of the destination
63 * image.
64 *
65 * We also offer a "force to grayscale" option, which simply discards the
66 * chrominance channels of a YCbCr image.  This is lossless in the sense that
67 * the luminance channel is preserved exactly.  It's not the same kind of
68 * thing as the rotate/flip transformations, but it's convenient to handle it
69 * as part of this package, mainly because the transformation routines have to
70 * be aware of the option to know how many components to work on.
71 */
72
73
74/* Short forms of external names for systems with brain-damaged linkers. */
75
76#ifdef NEED_SHORT_EXTERNAL_NAMES
77#define jtransform_parse_crop_spec      jTrParCrop
78#define jtransform_request_workspace    jTrRequest
79#define jtransform_adjust_parameters    jTrAdjust
80#define jtransform_execute_transform    jTrExec
81#define jtransform_perfect_transform    jTrPerfect
82#define jcopy_markers_setup             jCMrkSetup
83#define jcopy_markers_execute           jCMrkExec
84#endif /* NEED_SHORT_EXTERNAL_NAMES */
85
86
87/*
88 * Codes for supported types of image transformations.
89 */
90
91typedef enum {
92        JXFORM_NONE,            /* no transformation */
93        JXFORM_FLIP_H,          /* horizontal flip */
94        JXFORM_FLIP_V,          /* vertical flip */
95        JXFORM_TRANSPOSE,       /* transpose across UL-to-LR axis */
96        JXFORM_TRANSVERSE,      /* transpose across UR-to-LL axis */
97        JXFORM_ROT_90,          /* 90-degree clockwise rotation */
98        JXFORM_ROT_180,         /* 180-degree rotation */
99        JXFORM_ROT_270          /* 270-degree clockwise (or 90 ccw) */
100} JXFORM_CODE;
101
102/*
103 * Codes for crop parameters, which can individually be unspecified,
104 * positive, or negative.  (Negative width or height makes no sense, though.)
105 */
106
107typedef enum {
108        JCROP_UNSET,
109        JCROP_POS,
110        JCROP_NEG
111} JCROP_CODE;
112
113/*
114 * Transform parameters struct.
115 * NB: application must not change any elements of this struct after
116 * calling jtransform_request_workspace.
117 */
118
119typedef struct {
120  /* Options: set by caller */
121  JXFORM_CODE transform;        /* image transform operator */
122  boolean perfect;              /* if TRUE, fail if partial MCUs are requested */
123  boolean trim;                 /* if TRUE, trim partial MCUs as needed */
124  boolean force_grayscale;      /* if TRUE, convert color image to grayscale */
125  boolean crop;                 /* if TRUE, crop source image */
126
127  /* Crop parameters: application need not set these unless crop is TRUE.
128   * These can be filled in by jtransform_parse_crop_spec().
129   */
130  JDIMENSION crop_width;        /* Width of selected region */
131  JCROP_CODE crop_width_set;
132  JDIMENSION crop_height;       /* Height of selected region */
133  JCROP_CODE crop_height_set;
134  JDIMENSION crop_xoffset;      /* X offset of selected region */
135  JCROP_CODE crop_xoffset_set;  /* (negative measures from right edge) */
136  JDIMENSION crop_yoffset;      /* Y offset of selected region */
137  JCROP_CODE crop_yoffset_set;  /* (negative measures from bottom edge) */
138
139  /* Internal workspace: caller should not touch these */
140  int num_components;           /* # of components in workspace */
141  jvirt_barray_ptr * workspace_coef_arrays; /* workspace for transformations */
142  JDIMENSION output_width;      /* cropped destination dimensions */
143  JDIMENSION output_height;
144  JDIMENSION x_crop_offset;     /* destination crop offsets measured in iMCUs */
145  JDIMENSION y_crop_offset;
146  int max_h_samp_factor;        /* destination iMCU size */
147  int max_v_samp_factor;
148} jpeg_transform_info;
149
150
151#if TRANSFORMS_SUPPORTED
152
153/* Parse a crop specification (written in X11 geometry style) */
154EXTERN(boolean) jtransform_parse_crop_spec
155        JPP((jpeg_transform_info *info, const char *spec));
156/* Request any required workspace */
157EXTERN(void) jtransform_request_workspace
158        JPP((j_decompress_ptr srcinfo, jpeg_transform_info *info));
159/* Adjust output image parameters */
160EXTERN(jvirt_barray_ptr *) jtransform_adjust_parameters
161        JPP((j_decompress_ptr srcinfo, j_compress_ptr dstinfo,
162             jvirt_barray_ptr *src_coef_arrays,
163             jpeg_transform_info *info));
164/* Execute the actual transformation, if any */
165EXTERN(void) jtransform_execute_transform
166        JPP((j_decompress_ptr srcinfo, j_compress_ptr dstinfo,
167             jvirt_barray_ptr *src_coef_arrays,
168             jpeg_transform_info *info));
169/* Determine whether lossless transformation is perfectly
170 * possible for a specified image and transformation.
171 */
172EXTERN(boolean) jtransform_perfect_transform
173        JPP((JDIMENSION image_width, JDIMENSION image_height,
174             int MCU_width, int MCU_height,
175             JXFORM_CODE transform));
176
177/* jtransform_execute_transform used to be called
178 * jtransform_execute_transformation, but some compilers complain about
179 * routine names that long.  This macro is here to avoid breaking any
180 * old source code that uses the original name...
181 */
182#define jtransform_execute_transformation       jtransform_execute_transform
183
184#endif /* TRANSFORMS_SUPPORTED */
185
186
187/*
188 * Support for copying optional markers from source to destination file.
189 */
190
191typedef enum {
192        JCOPYOPT_NONE,          /* copy no optional markers */
193        JCOPYOPT_COMMENTS,      /* copy only comment (COM) markers */
194        JCOPYOPT_ALL            /* copy all optional markers */
195} JCOPY_OPTION;
196
197#define JCOPYOPT_DEFAULT  JCOPYOPT_COMMENTS     /* recommended default */
198
199/* Setup decompression object to save desired markers in memory */
200EXTERN(void) jcopy_markers_setup
201        JPP((j_decompress_ptr srcinfo, JCOPY_OPTION option));
202/* Copy markers saved in the given source object to the destination object */
203EXTERN(void) jcopy_markers_execute
204        JPP((j_decompress_ptr srcinfo, j_compress_ptr dstinfo,
205             JCOPY_OPTION option));
Note: See TracBrowser for help on using the repository browser.