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 97 typedef 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 */ 113 114 typedef 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 */ 126 127 typedef 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) */ 162 EXTERN(boolean) jtransform_parse_crop_spec 163 JPP((jpeg_transform_info *info, const char *spec)); 164 /* Request any required workspace */ 165 EXTERN(boolean) jtransform_request_workspace 166 JPP((j_decompress_ptr srcinfo, jpeg_transform_info *info)); 167 /* Adjust output image parameters */ 168 EXTERN(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 */ 173 EXTERN(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 */ 180 EXTERN(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 */ 198 199 typedef 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 */ 208 EXTERN(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 */ 211 EXTERN(void) jcopy_markers_execute 212 JPP((j_decompress_ptr srcinfo, j_compress_ptr dstinfo, 213 JCOPY_OPTION option)); 214