/src/FreeImage/Source/LibJPEG/transupp.h

  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
 80/* Short forms of external names for systems with brain-damaged linkers. */
 81
 82#ifdef NEED_SHORT_EXTERNAL_NAMES
 83#define jtransform_parse_crop_spec	jTrParCrop
 84#define jtransform_request_workspace	jTrRequest
 85#define jtransform_adjust_parameters	jTrAdjust
 86#define jtransform_execute_transform	jTrExec
 87#define jtransform_perfect_transform	jTrPerfect
 88#define jcopy_markers_setup		jCMrkSetup
 89#define jcopy_markers_execute		jCMrkExec
 90#endif /* NEED_SHORT_EXTERNAL_NAMES */
 91
 92
 93/*
 94 * Codes for supported types of image transformations.
 95 */
 96
 97typedef enum {
 98	JXFORM_NONE,		/* no transformation */
 99	JXFORM_FLIP_H,		/* horizontal flip */
100	JXFORM_FLIP_V,		/* vertical flip */
101	JXFORM_TRANSPOSE,	/* transpose across UL-to-LR axis */
102	JXFORM_TRANSVERSE,	/* transpose across UR-to-LL axis */
103	JXFORM_ROT_90,		/* 90-degree clockwise rotation */
104	JXFORM_ROT_180,		/* 180-degree rotation */
105	JXFORM_ROT_270		/* 270-degree clockwise (or 90 ccw) */
106} JXFORM_CODE;
107
108/*
109 * Codes for crop parameters, which can individually be unspecified,
110 * positive or negative for xoffset or yoffset,
111 * positive or forced for width or height.
112 */
113
114typedef enum {
115        JCROP_UNSET,
116        JCROP_POS,
117        JCROP_NEG,
118        JCROP_FORCE
119} JCROP_CODE;
120
121/*
122 * Transform parameters struct.
123 * NB: application must not change any elements of this struct after
124 * calling jtransform_request_workspace.
125 */
126
127typedef struct {
128  /* Options: set by caller */
129  JXFORM_CODE transform;	/* image transform operator */
130  boolean perfect;		/* if TRUE, fail if partial MCUs are requested */
131  boolean trim;			/* if TRUE, trim partial MCUs as needed */
132  boolean force_grayscale;	/* if TRUE, convert color image to grayscale */
133  boolean crop;			/* if TRUE, crop source image */
134
135  /* Crop parameters: application need not set these unless crop is TRUE.
136   * These can be filled in by jtransform_parse_crop_spec().
137   */
138  JDIMENSION crop_width;	/* Width of selected region */
139  JCROP_CODE crop_width_set;	/* (forced disables adjustment) */
140  JDIMENSION crop_height;	/* Height of selected region */
141  JCROP_CODE crop_height_set;	/* (forced disables adjustment) */
142  JDIMENSION crop_xoffset;	/* X offset of selected region */
143  JCROP_CODE crop_xoffset_set;	/* (negative measures from right edge) */
144  JDIMENSION crop_yoffset;	/* Y offset of selected region */
145  JCROP_CODE crop_yoffset_set;	/* (negative measures from bottom edge) */
146
147  /* Internal workspace: caller should not touch these */
148  int num_components;		/* # of components in workspace */
149  jvirt_barray_ptr * workspace_coef_arrays; /* workspace for transformations */
150  JDIMENSION output_width;	/* cropped destination dimensions */
151  JDIMENSION output_height;
152  JDIMENSION x_crop_offset;	/* destination crop offsets measured in iMCUs */
153  JDIMENSION y_crop_offset;
154  int iMCU_sample_width;	/* destination iMCU size */
155  int iMCU_sample_height;
156} jpeg_transform_info;
157
158
159#if TRANSFORMS_SUPPORTED
160
161/* Parse a crop specification (written in X11 geometry style) */
162EXTERN(boolean) jtransform_parse_crop_spec
163	JPP((jpeg_transform_info *info, const char *spec));
164/* Request any required workspace */
165EXTERN(boolean) jtransform_request_workspace
166	JPP((j_decompress_ptr srcinfo, jpeg_transform_info *info));
167/* Adjust output image parameters */
168EXTERN(jvirt_barray_ptr *) jtransform_adjust_parameters
169	JPP((j_decompress_ptr srcinfo, j_compress_ptr dstinfo,
170	     jvirt_barray_ptr *src_coef_arrays,
171	     jpeg_transform_info *info));
172/* Execute the actual transformation, if any */
173EXTERN(void) jtransform_execute_transform
174	JPP((j_decompress_ptr srcinfo, j_compress_ptr dstinfo,
175	     jvirt_barray_ptr *src_coef_arrays,
176	     jpeg_transform_info *info));
177/* Determine whether lossless transformation is perfectly
178 * possible for a specified image and transformation.
179 */
180EXTERN(boolean) jtransform_perfect_transform
181	JPP((JDIMENSION image_width, JDIMENSION image_height,
182	     int MCU_width, int MCU_height,
183	     JXFORM_CODE transform));
184
185/* jtransform_execute_transform used to be called
186 * jtransform_execute_transformation, but some compilers complain about
187 * routine names that long.  This macro is here to avoid breaking any
188 * old source code that uses the original name...
189 */
190#define jtransform_execute_transformation	jtransform_execute_transform
191
192#endif /* TRANSFORMS_SUPPORTED */
193
194
195/*
196 * Support for copying optional markers from source to destination file.
197 */
198
199typedef 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#define JCOPYOPT_DEFAULT  JCOPYOPT_COMMENTS	/* recommended default */
206
207/* Setup decompression object to save desired markers in memory */
208EXTERN(void) jcopy_markers_setup
209	JPP((j_decompress_ptr srcinfo, JCOPY_OPTION option));
210/* Copy markers saved in the given source object to the destination object */
211EXTERN(void) jcopy_markers_execute
212	JPP((j_decompress_ptr srcinfo, j_compress_ptr dstinfo,
213	     JCOPY_OPTION option));