File indexing completed on 2024-05-12 04:19:44
0001 /* 0002 * transupp.h 0003 * 0004 * Copyright (C) 1997, Thomas G. Lane. 0005 * This file is part of the Independent JPEG Group's software. 0006 * For conditions of distribution and use, see the accompanying README file. 0007 * 0008 * This file contains declarations for image transformation routines and 0009 * other utility code used by the jpegtran sample application. These are 0010 * NOT part of the core JPEG library. But we keep these routines separate 0011 * from jpegtran.c to ease the task of maintaining jpegtran-like programs 0012 * that have other user interfaces. 0013 * 0014 * NOTE: all the routines declared here have very specific requirements 0015 * about when they are to be executed during the reading and writing of the 0016 * source and destination files. See the comments in transupp.c, or see 0017 * jpegtran.c for an example of correct usage. 0018 */ 0019 0020 #ifndef TRANSUPP_H 0021 #define TRANSUPP_H 0022 0023 /* If you happen not to want the image transform support, disable it here */ 0024 #ifndef TRANSFORMS_SUPPORTED 0025 #define TRANSFORMS_SUPPORTED 1 /* 0 disables transform code */ 0026 #endif 0027 0028 /* Short forms of external names for systems with brain-damaged linkers. */ 0029 0030 #ifdef NEED_SHORT_EXTERNAL_NAMES 0031 #define jtransform_request_workspace jTrRequest 0032 #define jtransform_adjust_parameters jTrAdjust 0033 #define jtransform_execute_transformation jTrExec 0034 #define jcopy_markers_setup jCMrkSetup 0035 #define jcopy_markers_execute jCMrkExec 0036 #endif /* NEED_SHORT_EXTERNAL_NAMES */ 0037 0038 /* 0039 * Codes for supported types of image transformations. 0040 */ 0041 0042 typedef enum { 0043 JXFORM_NONE, /* no transformation */ 0044 JXFORM_FLIP_H, /* horizontal flip */ 0045 JXFORM_FLIP_V, /* vertical flip */ 0046 JXFORM_TRANSPOSE, /* transpose across UL-to-LR axis */ 0047 JXFORM_TRANSVERSE, /* transpose across UR-to-LL axis */ 0048 JXFORM_ROT_90, /* 90-degree clockwise rotation */ 0049 JXFORM_ROT_180, /* 180-degree rotation */ 0050 JXFORM_ROT_270 /* 270-degree clockwise (or 90 ccw) */ 0051 } JXFORM_CODE; 0052 0053 /* 0054 * Although rotating and flipping data expressed as DCT coefficients is not 0055 * hard, there is an asymmetry in the JPEG format specification for images 0056 * whose dimensions aren't multiples of the iMCU size. The right and bottom 0057 * image edges are padded out to the next iMCU boundary with junk data; but 0058 * no padding is possible at the top and left edges. If we were to flip 0059 * the whole image including the pad data, then pad garbage would become 0060 * visible at the top and/or left, and real pixels would disappear into the 0061 * pad margins --- perhaps permanently, since encoders & decoders may not 0062 * bother to preserve DCT blocks that appear to be completely outside the 0063 * nominal image area. So, we have to exclude any partial iMCUs from the 0064 * basic transformation. 0065 * 0066 * Transpose is the only transformation that can handle partial iMCUs at the 0067 * right and bottom edges completely cleanly. flip_h can flip partial iMCUs 0068 * at the bottom, but leaves any partial iMCUs at the right edge untouched. 0069 * Similarly flip_v leaves any partial iMCUs at the bottom edge untouched. 0070 * The other transforms are defined as combinations of these basic transforms 0071 * and process edge blocks in a way that preserves the equivalence. 0072 * 0073 * The "trim" option causes untransformable partial iMCUs to be dropped; 0074 * this is not strictly lossless, but it usually gives the best-looking 0075 * result for odd-size images. Note that when this option is active, 0076 * the expected mathematical equivalences between the transforms may not hold. 0077 * (For example, -rot 270 -trim trims only the bottom edge, but -rot 90 -trim 0078 * followed by -rot 180 -trim trims both edges.) 0079 * 0080 * We also offer a "force to grayscale" option, which simply discards the 0081 * chrominance channels of a YCbCr image. This is lossless in the sense that 0082 * the luminance channel is preserved exactly. It's not the same kind of 0083 * thing as the rotate/flip transformations, but it's convenient to handle it 0084 * as part of this package, mainly because the transformation routines have to 0085 * be aware of the option to know how many components to work on. 0086 */ 0087 0088 typedef struct { 0089 /* Options: set by caller */ 0090 JXFORM_CODE transform; /* image transform operator */ 0091 boolean trim; /* if TRUE, trim partial MCUs as needed */ 0092 boolean force_grayscale; /* if TRUE, convert color image to grayscale */ 0093 0094 /* Internal workspace: caller should not touch these */ 0095 int num_components; /* # of components in workspace */ 0096 jvirt_barray_ptr * workspace_coef_arrays; /* workspace for transformations */ 0097 } jpeg_transform_info; 0098 0099 #if TRANSFORMS_SUPPORTED 0100 0101 /* Request any required workspace */ 0102 EXTERN(void) jtransform_request_workspace 0103 JPP((j_decompress_ptr srcinfo, jpeg_transform_info *info)); 0104 /* Adjust output image parameters */ 0105 EXTERN(jvirt_barray_ptr *) jtransform_adjust_parameters 0106 JPP((j_decompress_ptr srcinfo, j_compress_ptr dstinfo, 0107 jvirt_barray_ptr *src_coef_arrays, 0108 jpeg_transform_info *info)); 0109 /* Execute the actual transformation, if any */ 0110 EXTERN(void) jtransform_execute_transformation 0111 JPP((j_decompress_ptr srcinfo, j_compress_ptr dstinfo, 0112 jvirt_barray_ptr *src_coef_arrays, 0113 jpeg_transform_info *info)); 0114 0115 #endif /* TRANSFORMS_SUPPORTED */ 0116 0117 /* 0118 * Support for copying optional markers from source to destination file. 0119 */ 0120 0121 typedef enum { 0122 JCOPYOPT_NONE, /* copy no optional markers */ 0123 JCOPYOPT_COMMENTS, /* copy only comment (COM) markers */ 0124 JCOPYOPT_ALL /* copy all optional markers */ 0125 } JCOPY_OPTION; 0126 0127 #define JCOPYOPT_DEFAULT JCOPYOPT_COMMENTS /* recommended default */ 0128 0129 /* Setup decompression object to save desired markers in memory */ 0130 EXTERN(void) jcopy_markers_setup 0131 JPP((j_decompress_ptr srcinfo, JCOPY_OPTION option)); 0132 /* Copy markers saved in the given source object to the destination object */ 0133 EXTERN(void) jcopy_markers_execute 0134 JPP((j_decompress_ptr srcinfo, j_compress_ptr dstinfo, 0135 JCOPY_OPTION option)); 0136 0137 #endif 0138