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Merge from eCos master repository on 2002-05-20-20:11:54-BST
author jlarmour
date Mon, 20 May 2002 22:19:26 +0000
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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
40 typedef 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
86 typedef 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 */
101 EXTERN(void) jtransform_request_workspace
102 JPP((j_decompress_ptr srcinfo, jpeg_transform_info *info));
103 /* Adjust output image parameters */
104 EXTERN(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 */
109 EXTERN(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
121 typedef 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 */
130 EXTERN(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 */
133 EXTERN(void) jcopy_markers_execute
134 JPP((j_decompress_ptr srcinfo, j_compress_ptr dstinfo,
135 JCOPY_OPTION option));