1 /* 2 * transupp.h 3 * 4 * Copyright (C) 1997-2013, 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 * 65 * We also provide a lossless-resize option, which is kind of a lossless-crop 66 * operation in the DCT coefficient block domain - it discards higher-order 67 * coefficients and losslessly preserves lower-order coefficients of a 68 * sub-block. 69 * 70 * Rotate/flip transform, resize, and crop can be requested together in a 71 * single invocation. The crop is applied last --- that is, the crop region 72 * is specified in terms of the destination image after transform/resize. 73 * 74 * We also offer a "force to grayscale" option, which simply discards the 75 * chrominance channels of a YCbCr image. This is lossless in the sense that 76 * the luminance channel is preserved exactly. It's not the same kind of 77 * thing as the rotate/flip transformations, but it's convenient to handle it 78 * as part of this package, mainly because the transformation routines have to 79 * be aware of the option to know how many components to work on. 80 */ 81 82 83 /* Short forms of external names for systems with brain-damaged linkers. */ 84 85 #ifdef NEED_SHORT_EXTERNAL_NAMES 86 #define jtransform_parse_crop_spec jTrParCrop 87 #define jtransform_request_workspace jTrRequest 88 #define jtransform_adjust_parameters jTrAdjust 89 #define jtransform_execute_transform jTrExec 90 #define jtransform_perfect_transform jTrPerfect 91 #define jcopy_markers_setup jCMrkSetup 92 #define jcopy_markers_execute jCMrkExec 93 #endif /* NEED_SHORT_EXTERNAL_NAMES */ 94 95 96 /* 97 * Codes for supported types of image transformations. 98 */ 99 100 typedef enum { 101 JXFORM_NONE, /* no transformation */ 102 JXFORM_FLIP_H, /* horizontal flip */ 103 JXFORM_FLIP_V, /* vertical flip */ 104 JXFORM_TRANSPOSE, /* transpose across UL-to-LR axis */ 105 JXFORM_TRANSVERSE, /* transpose across UR-to-LL axis */ 106 JXFORM_ROT_90, /* 90-degree clockwise rotation */ 107 JXFORM_ROT_180, /* 180-degree rotation */ 108 JXFORM_ROT_270, /* 270-degree clockwise (or 90 ccw) */ 109 JXFORM_WIPE /* wipe */ 110 } JXFORM_CODE; 111 112 /* 113 * Codes for crop parameters, which can individually be unspecified, 114 * positive or negative for xoffset or yoffset, 115 * positive or forced for width or height. 116 */ 117 118 typedef enum { 119 JCROP_UNSET, 120 JCROP_POS, 121 JCROP_NEG, 122 JCROP_FORCE 123 } JCROP_CODE; 124 125 /* 126 * Transform parameters struct. 127 * NB: application must not change any elements of this struct after 128 * calling jtransform_request_workspace. 129 */ 130 131 typedef struct { 132 /* Options: set by caller */ 133 JXFORM_CODE transform; /* image transform operator */ 134 boolean perfect; /* if TRUE, fail if partial MCUs are requested */ 135 boolean trim; /* if TRUE, trim partial MCUs as needed */ 136 boolean force_grayscale; /* if TRUE, convert color image to grayscale */ 137 boolean crop; /* if TRUE, crop or wipe source image */ 138 139 /* Crop parameters: application need not set these unless crop is TRUE. 140 * These can be filled in by jtransform_parse_crop_spec(). 141 */ 142 JDIMENSION crop_width; /* Width of selected region */ 143 JCROP_CODE crop_width_set; /* (forced disables adjustment) */ 144 JDIMENSION crop_height; /* Height of selected region */ 145 JCROP_CODE crop_height_set; /* (forced disables adjustment) */ 146 JDIMENSION crop_xoffset; /* X offset of selected region */ 147 JCROP_CODE crop_xoffset_set; /* (negative measures from right edge) */ 148 JDIMENSION crop_yoffset; /* Y offset of selected region */ 149 JCROP_CODE crop_yoffset_set; /* (negative measures from bottom edge) */ 150 151 /* Internal workspace: caller should not touch these */ 152 int num_components; /* # of components in workspace */ 153 jvirt_barray_ptr * workspace_coef_arrays; /* workspace for transformations */ 154 JDIMENSION output_width; /* cropped destination dimensions */ 155 JDIMENSION output_height; 156 JDIMENSION x_crop_offset; /* destination crop offsets measured in iMCUs */ 157 JDIMENSION y_crop_offset; 158 JDIMENSION drop_width; /* drop/wipe dimensions measured in iMCUs */ 159 JDIMENSION drop_height; 160 int iMCU_sample_width; /* destination iMCU size */ 161 int iMCU_sample_height; 162 } jpeg_transform_info; 163 164 165 #if TRANSFORMS_SUPPORTED 166 167 /* Parse a crop specification (written in X11 geometry style) */ 168 EXTERN(boolean) jtransform_parse_crop_spec 169 JPP((jpeg_transform_info *info, const char *spec)); 170 /* Request any required workspace */ 171 EXTERN(boolean) jtransform_request_workspace 172 JPP((j_decompress_ptr srcinfo, jpeg_transform_info *info)); 173 /* Adjust output image parameters */ 174 EXTERN(jvirt_barray_ptr *) jtransform_adjust_parameters 175 JPP((j_decompress_ptr srcinfo, j_compress_ptr dstinfo, 176 jvirt_barray_ptr *src_coef_arrays, 177 jpeg_transform_info *info)); 178 /* Execute the actual transformation, if any */ 179 EXTERN(void) jtransform_execute_transform 180 JPP((j_decompress_ptr srcinfo, j_compress_ptr dstinfo, 181 jvirt_barray_ptr *src_coef_arrays, 182 jpeg_transform_info *info)); 183 /* Determine whether lossless transformation is perfectly 184 * possible for a specified image and transformation. 185 */ 186 EXTERN(boolean) jtransform_perfect_transform 187 JPP((JDIMENSION image_width, JDIMENSION image_height, 188 int MCU_width, int MCU_height, 189 JXFORM_CODE transform)); 190 191 /* jtransform_execute_transform used to be called 192 * jtransform_execute_transformation, but some compilers complain about 193 * routine names that long. This macro is here to avoid breaking any 194 * old source code that uses the original name... 195 */ 196 #define jtransform_execute_transformation jtransform_execute_transform 197 198 #endif /* TRANSFORMS_SUPPORTED */ 199 200 201 /* 202 * Support for copying optional markers from source to destination file. 203 */ 204 205 typedef enum { 206 JCOPYOPT_NONE, /* copy no optional markers */ 207 JCOPYOPT_COMMENTS, /* copy only comment (COM) markers */ 208 JCOPYOPT_ALL /* copy all optional markers */ 209 } JCOPY_OPTION; 210 211 #define JCOPYOPT_DEFAULT JCOPYOPT_COMMENTS /* recommended default */ 212 213 /* Setup decompression object to save desired markers in memory */ 214 EXTERN(void) jcopy_markers_setup 215 JPP((j_decompress_ptr srcinfo, JCOPY_OPTION option)); 216 /* Copy markers saved in the given source object to the destination object */ 217 EXTERN(void) jcopy_markers_execute 218 JPP((j_decompress_ptr srcinfo, j_compress_ptr dstinfo, 219 JCOPY_OPTION option)); 220