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)); 136
