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transupp.h
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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) */
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 */
96 
97 
98 #if TRANSFORMS_SUPPORTED
99 
100 /* Request any required workspace */
101 EXTERN(void) jtransform_request_workspace
103 /* Adjust output image parameters */
104 EXTERN(jvirt_barray_ptr *) jtransform_adjust_parameters
106  jvirt_barray_ptr *src_coef_arrays,
108 /* Execute the actual transformation, if any */
109 EXTERN(void) jtransform_execute_transformation
111  jvirt_barray_ptr *src_coef_arrays,
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 */
126 
127 #define JCOPYOPT_DEFAULT JCOPYOPT_COMMENTS /* recommended default */
128 
129 /* Setup decompression object to save desired markers in memory */
132 /* Copy markers saved in the given source object to the destination object */
#define info
Definition: dviinfo.c:42
#define JPP(arglist)
Definition: jpeglib.h:818
void jcopy_markers_execute(j_decompress_ptr srcinfo, j_compress_ptr dstinfo, JCOPY_OPTION option)
Definition: transupp.c:886
void jcopy_markers_setup(j_decompress_ptr srcinfo, JCOPY_OPTION option)
Definition: transupp.c:861
JXFORM_CODE
Definition: transupp.h:40
@ JXFORM_FLIP_H
Definition: transupp.h:42
@ JXFORM_ROT_270
Definition: transupp.h:48
@ JXFORM_TRANSPOSE
Definition: transupp.h:44
@ JXFORM_TRANSVERSE
Definition: transupp.h:45
@ JXFORM_NONE
Definition: transupp.h:41
@ JXFORM_ROT_180
Definition: transupp.h:47
@ JXFORM_FLIP_V
Definition: transupp.h:43
@ JXFORM_ROT_90
Definition: transupp.h:46
EXTERN(void) jcopy_markers_setup JPP((j_decompress_ptr srcinfo
JCOPY_OPTION
Definition: transupp.h:121
@ JCOPYOPT_NONE
Definition: transupp.h:122
@ JCOPYOPT_COMMENTS
Definition: transupp.h:123
@ JCOPYOPT_ALL
Definition: transupp.h:124
j_compress_ptr dstinfo
Definition: transupp.h:134
boolean force_grayscale
Definition: transupp.h:90
JXFORM_CODE transform
Definition: transupp.h:88
jvirt_barray_ptr * workspace_coef_arrays
Definition: transupp.h:94
Definition: getopt.h:95