1 /* 2 * transupp.h 3 * 4 * Copyright (C) 1997-2019, 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 current JPEG format: the 55 * upper left corner of the selected region must fall on an iMCU boundary. If 56 * this does not hold for the given crop parameters, we silently move the upper 57 * left corner up and/or left to make it so, simultaneously increasing the 58 * region 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 * A complementary lossless-wipe option is provided to discard (gray out) data 63 * inside a given image region while losslessly preserving what is outside. 64 * Another option is lossless-drop, which replaces data at a given image 65 * position by another image. Both source images must have the same 66 * subsampling values. It is best if they also have the same quantization, 67 * otherwise quantization adaption occurs. The trim option can be used with 68 * the drop option to requantize the drop file to the source file. 69 * 70 * We also provide a lossless-resize option, which is kind of a lossless-crop 71 * operation in the DCT coefficient block domain - it discards higher-order 72 * coefficients and losslessly preserves lower-order coefficients of a 73 * sub-block. 74 * 75 * Rotate/flip transform, resize, and crop can be requested together in a 76 * single invocation. The crop is applied last --- that is, the crop region 77 * is specified in terms of the destination image after transform/resize. 78 * 79 * We also offer a "force to grayscale" option, which simply discards the 80 * chrominance channels of a YCbCr image. This is lossless in the sense that 81 * the luminance channel is preserved exactly. It's not the same kind of 82 * thing as the rotate/flip transformations, but it's convenient to handle it 83 * as part of this package, mainly because the transformation routines have to 84 * be aware of the option to know how many components to work on. 85 */ 86 87 88 /* Short forms of external names for systems with brain-damaged linkers. */ 89 90 #ifdef NEED_SHORT_EXTERNAL_NAMES 91 #define jtransform_parse_crop_spec jTrParCrop 92 #define jtransform_request_workspace jTrRequest 93 #define jtransform_adjust_parameters jTrAdjust 94 #define jtransform_execute_transform jTrExec 95 #define jtransform_perfect_transform jTrPerfect 96 #define jcopy_markers_setup jCMrkSetup 97 #define jcopy_markers_execute jCMrkExec 98 #endif /* NEED_SHORT_EXTERNAL_NAMES */ 99 100 101 /* 102 * Codes for supported types of image transformations. 103 */ 104 105 typedef enum { 106 JXFORM_NONE, /* no transformation */ 107 JXFORM_FLIP_H, /* horizontal flip */ 108 JXFORM_FLIP_V, /* vertical flip */ 109 JXFORM_TRANSPOSE, /* transpose across UL-to-LR axis */ 110 JXFORM_TRANSVERSE, /* transpose across UR-to-LL axis */ 111 JXFORM_ROT_90, /* 90-degree clockwise rotation */ 112 JXFORM_ROT_180, /* 180-degree rotation */ 113 JXFORM_ROT_270, /* 270-degree clockwise (or 90 ccw) */ 114 JXFORM_WIPE, /* wipe */ 115 JXFORM_DROP /* drop */ 116 } JXFORM_CODE; 117 118 /* 119 * Codes for crop parameters, which can individually be unspecified, 120 * positive or negative for xoffset or yoffset, 121 * positive or force or reflect for width or height. 122 */ 123 124 typedef enum { 125 JCROP_UNSET, 126 JCROP_POS, 127 JCROP_NEG, 128 JCROP_FORCE, 129 JCROP_REFLECT 130 } JCROP_CODE; 131 132 /* 133 * Transform parameters struct. 134 * NB: application must not change any elements of this struct after 135 * calling jtransform_request_workspace. 136 */ 137 138 typedef struct { 139 /* Options: set by caller */ 140 JXFORM_CODE transform; /* image transform operator */ 141 boolean perfect; /* if TRUE, fail if partial MCUs are requested */ 142 boolean trim; /* if TRUE, trim partial MCUs as needed */ 143 boolean force_grayscale; /* if TRUE, convert color image to grayscale */ 144 boolean crop; /* if TRUE, crop or wipe source image, or drop */ 145 146 /* Crop parameters: application need not set these unless crop is TRUE. 147 * These can be filled in by jtransform_parse_crop_spec(). 148 */ 149 JDIMENSION crop_width; /* Width of selected region */ 150 JCROP_CODE crop_width_set; /* (force disables adjustment) */ 151 JDIMENSION crop_height; /* Height of selected region */ 152 JCROP_CODE crop_height_set; /* (force disables adjustment) */ 153 JDIMENSION crop_xoffset; /* X offset of selected region */ 154 JCROP_CODE crop_xoffset_set; /* (negative measures from right edge) */ 155 JDIMENSION crop_yoffset; /* Y offset of selected region */ 156 JCROP_CODE crop_yoffset_set; /* (negative measures from bottom edge) */ 157 158 /* Drop parameters: set by caller for drop request */ 159 j_decompress_ptr drop_ptr; 160 jvirt_barray_ptr * drop_coef_arrays; 161 162 /* Internal workspace: caller should not touch these */ 163 int num_components; /* # of components in workspace */ 164 jvirt_barray_ptr * workspace_coef_arrays; /* workspace for transformations */ 165 JDIMENSION output_width; /* cropped destination dimensions */ 166 JDIMENSION output_height; 167 JDIMENSION x_crop_offset; /* destination crop offsets measured in iMCUs */ 168 JDIMENSION y_crop_offset; 169 JDIMENSION drop_width; /* drop/wipe dimensions measured in iMCUs */ 170 JDIMENSION drop_height; 171 int iMCU_sample_width; /* destination iMCU size */ 172 int iMCU_sample_height; 173 } jpeg_transform_info; 174 175 176 #if TRANSFORMS_SUPPORTED 177 178 /* Parse a crop specification (written in X11 geometry style) */ 179 EXTERN(boolean) jtransform_parse_crop_spec 180 JPP((jpeg_transform_info *info, const char *spec)); 181 /* Request any required workspace */ 182 EXTERN(boolean) jtransform_request_workspace 183 JPP((j_decompress_ptr srcinfo, jpeg_transform_info *info)); 184 /* Adjust output image parameters */ 185 EXTERN(jvirt_barray_ptr *) jtransform_adjust_parameters 186 JPP((j_decompress_ptr srcinfo, j_compress_ptr dstinfo, 187 jvirt_barray_ptr *src_coef_arrays, 188 jpeg_transform_info *info)); 189 /* Execute the actual transformation, if any */ 190 EXTERN(void) jtransform_execute_transform 191 JPP((j_decompress_ptr srcinfo, j_compress_ptr dstinfo, 192 jvirt_barray_ptr *src_coef_arrays, 193 jpeg_transform_info *info)); 194 /* Determine whether lossless transformation is perfectly 195 * possible for a specified image and transformation. 196 */ 197 EXTERN(boolean) jtransform_perfect_transform 198 JPP((JDIMENSION image_width, JDIMENSION image_height, 199 int MCU_width, int MCU_height, 200 JXFORM_CODE transform)); 201 202 /* jtransform_execute_transform used to be called 203 * jtransform_execute_transformation, but some compilers complain about 204 * routine names that long. This macro is here to avoid breaking any 205 * old source code that uses the original name... 206 */ 207 #define jtransform_execute_transformation jtransform_execute_transform 208 209 #endif /* TRANSFORMS_SUPPORTED */ 210 211 212 /* 213 * Support for copying optional markers from source to destination file. 214 */ 215 216 typedef enum { 217 JCOPYOPT_NONE, /* copy no optional markers */ 218 JCOPYOPT_COMMENTS, /* copy only comment (COM) markers */ 219 JCOPYOPT_ALL /* copy all optional markers */ 220 } JCOPY_OPTION; 221 222 #define JCOPYOPT_DEFAULT JCOPYOPT_COMMENTS /* recommended default */ 223 224 /* Setup decompression object to save desired markers in memory */ 225 EXTERN(void) jcopy_markers_setup 226 JPP((j_decompress_ptr srcinfo, JCOPY_OPTION option)); 227 /* Copy markers saved in the given source object to the destination object */ 228 EXTERN(void) jcopy_markers_execute 229 JPP((j_decompress_ptr srcinfo, j_compress_ptr dstinfo, 230 JCOPY_OPTION option)); 231