source: trunk/libjpeg/transupp.h @ 15

Last change on this file since 15 was 15, checked in by Eugene Romanenko, 15 years ago

needed libs update

File size: 5.8 KB
Line 
1/*
2 * transupp.h
3 *
4 * Copyright (C) 1997, 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/* Short forms of external names for systems with brain-damaged linkers. */
26
27#ifdef NEED_SHORT_EXTERNAL_NAMES
28#define jtransform_request_workspace            jTrRequest
29#define jtransform_adjust_parameters            jTrAdjust
30#define jtransform_execute_transformation       jTrExec
31#define jcopy_markers_setup                     jCMrkSetup
32#define jcopy_markers_execute                   jCMrkExec
33#endif /* NEED_SHORT_EXTERNAL_NAMES */
34
35
36/*
37 * Codes for supported types of image transformations.
38 */
39
40typedef enum {
41        JXFORM_NONE,            /* no transformation */
42        JXFORM_FLIP_H,          /* horizontal flip */
43        JXFORM_FLIP_V,          /* vertical flip */
44        JXFORM_TRANSPOSE,       /* transpose across UL-to-LR axis */
45        JXFORM_TRANSVERSE,      /* transpose across UR-to-LL axis */
46        JXFORM_ROT_90,          /* 90-degree clockwise rotation */
47        JXFORM_ROT_180,         /* 180-degree rotation */
48        JXFORM_ROT_270          /* 270-degree clockwise (or 90 ccw) */
49} JXFORM_CODE;
50
51/*
52 * Although rotating and flipping data expressed as DCT coefficients is not
53 * hard, there is an asymmetry in the JPEG format specification for images
54 * whose dimensions aren't multiples of the iMCU size.  The right and bottom
55 * image edges are padded out to the next iMCU boundary with junk data; but
56 * no padding is possible at the top and left edges.  If we were to flip
57 * the whole image including the pad data, then pad garbage would become
58 * visible at the top and/or left, and real pixels would disappear into the
59 * pad margins --- perhaps permanently, since encoders & decoders may not
60 * bother to preserve DCT blocks that appear to be completely outside the
61 * nominal image area.  So, we have to exclude any partial iMCUs from the
62 * basic transformation.
63 *
64 * Transpose is the only transformation that can handle partial iMCUs at the
65 * right and bottom edges completely cleanly.  flip_h can flip partial iMCUs
66 * at the bottom, but leaves any partial iMCUs at the right edge untouched.
67 * Similarly flip_v leaves any partial iMCUs at the bottom edge untouched.
68 * The other transforms are defined as combinations of these basic transforms
69 * and process edge blocks in a way that preserves the equivalence.
70 *
71 * The "trim" option causes untransformable partial iMCUs to be dropped;
72 * this is not strictly lossless, but it usually gives the best-looking
73 * result for odd-size images.  Note that when this option is active,
74 * the expected mathematical equivalences between the transforms may not hold.
75 * (For example, -rot 270 -trim trims only the bottom edge, but -rot 90 -trim
76 * followed by -rot 180 -trim trims both edges.)
77 *
78 * We also offer a "force to grayscale" option, which simply discards the
79 * chrominance channels of a YCbCr image.  This is lossless in the sense that
80 * the luminance channel is preserved exactly.  It's not the same kind of
81 * thing as the rotate/flip transformations, but it's convenient to handle it
82 * as part of this package, mainly because the transformation routines have to
83 * be aware of the option to know how many components to work on.
84 */
85
86typedef struct {
87  /* Options: set by caller */
88  JXFORM_CODE transform;        /* image transform operator */
89  boolean trim;                 /* if TRUE, trim partial MCUs as needed */
90  boolean force_grayscale;      /* if TRUE, convert color image to grayscale */
91
92  /* Internal workspace: caller should not touch these */
93  int num_components;           /* # of components in workspace */
94  jvirt_barray_ptr * workspace_coef_arrays; /* workspace for transformations */
95} jpeg_transform_info;
96
97
98#if TRANSFORMS_SUPPORTED
99
100/* Request any required workspace */
101EXTERN(void) jtransform_request_workspace
102        JPP((j_decompress_ptr srcinfo, jpeg_transform_info *info));
103/* Adjust output image parameters */
104EXTERN(jvirt_barray_ptr *) jtransform_adjust_parameters
105        JPP((j_decompress_ptr srcinfo, j_compress_ptr dstinfo,
106             jvirt_barray_ptr *src_coef_arrays,
107             jpeg_transform_info *info));
108/* Execute the actual transformation, if any */
109EXTERN(void) jtransform_execute_transformation
110        JPP((j_decompress_ptr srcinfo, j_compress_ptr dstinfo,
111             jvirt_barray_ptr *src_coef_arrays,
112             jpeg_transform_info *info));
113
114#endif /* TRANSFORMS_SUPPORTED */
115
116
117/*
118 * Support for copying optional markers from source to destination file.
119 */
120
121typedef enum {
122        JCOPYOPT_NONE,          /* copy no optional markers */
123        JCOPYOPT_COMMENTS,      /* copy only comment (COM) markers */
124        JCOPYOPT_ALL            /* copy all optional markers */
125} JCOPY_OPTION;
126
127#define JCOPYOPT_DEFAULT  JCOPYOPT_COMMENTS     /* recommended default */
128
129/* Setup decompression object to save desired markers in memory */
130EXTERN(void) jcopy_markers_setup
131        JPP((j_decompress_ptr srcinfo, JCOPY_OPTION option));
132/* Copy markers saved in the given source object to the destination object */
133EXTERN(void) jcopy_markers_execute
134        JPP((j_decompress_ptr srcinfo, j_compress_ptr dstinfo,
135             JCOPY_OPTION option));
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