1 /* 2 * transupp.h 3 * 4 * This file was part of the Independent JPEG Group's software: 5 * Copyright (C) 1997-2011, Thomas G. Lane, Guido Vollbeding. 6 * It was modified by The libjpeg-turbo Project to include only code relevant 7 * to libjpeg-turbo. 8 * For conditions of distribution and use, see the accompanying README file. 9 * 10 * This file contains declarations for image transformation routines and 11 * other utility code used by the jpegtran sample application. These are 12 * NOT part of the core JPEG library. But we keep these routines separate 13 * from jpegtran.c to ease the task of maintaining jpegtran-like programs 14 * that have other user interfaces. 15 * 16 * NOTE: all the routines declared here have very specific requirements 17 * about when they are to be executed during the reading and writing of the 18 * source and destination files. See the comments in transupp.c, or see 19 * jpegtran.c for an example of correct usage. 20 */ 21 22 /* If you happen not to want the image transform support, disable it here */ 23 #ifndef TRANSFORMS_SUPPORTED 24 #define TRANSFORMS_SUPPORTED 1 /* 0 disables transform code */ 25 #endif 26 27 /* 28 * Although rotating and flipping data expressed as DCT coefficients is not 29 * hard, there is an asymmetry in the JPEG format specification for images 30 * whose dimensions aren't multiples of the iMCU size. The right and bottom 31 * image edges are padded out to the next iMCU boundary with junk data; but 32 * no padding is possible at the top and left edges. If we were to flip 33 * the whole image including the pad data, then pad garbage would become 34 * visible at the top and/or left, and real pixels would disappear into the 35 * pad margins --- perhaps permanently, since encoders & decoders may not 36 * bother to preserve DCT blocks that appear to be completely outside the 37 * nominal image area. So, we have to exclude any partial iMCUs from the 38 * basic transformation. 39 * 40 * Transpose is the only transformation that can handle partial iMCUs at the 41 * right and bottom edges completely cleanly. flip_h can flip partial iMCUs 42 * at the bottom, but leaves any partial iMCUs at the right edge untouched. 43 * Similarly flip_v leaves any partial iMCUs at the bottom edge untouched. 44 * The other transforms are defined as combinations of these basic transforms 45 * and process edge blocks in a way that preserves the equivalence. 46 * 47 * The "trim" option causes untransformable partial iMCUs to be dropped; 48 * this is not strictly lossless, but it usually gives the best-looking 49 * result for odd-size images. Note that when this option is active, 50 * the expected mathematical equivalences between the transforms may not hold. 51 * (For example, -rot 270 -trim trims only the bottom edge, but -rot 90 -trim 52 * followed by -rot 180 -trim trims both edges.) 53 * 54 * We also offer a lossless-crop option, which discards data outside a given 55 * image region but losslessly preserves what is inside. Like the rotate and 56 * flip transforms, lossless crop is restricted by the JPEG format: the upper 57 * left corner of the selected region must fall on an iMCU boundary. If this 58 * does not hold for the given crop parameters, we silently move the upper left 59 * corner up and/or left to make it so, simultaneously increasing the region 60 * dimensions to keep the lower right crop corner unchanged. (Thus, the 61 * output image covers at least the requested region, but may cover more.) 62 * The adjustment of the region dimensions may be optionally disabled. 63 * 64 * We also provide a lossless-resize option, which is kind of a lossless-crop 65 * operation in the DCT coefficient block domain - it discards higher-order 66 * coefficients and losslessly preserves lower-order coefficients of a 67 * sub-block. 68 * 69 * Rotate/flip transform, resize, and crop can be requested together in a 70 * single invocation. The crop is applied last --- that is, the crop region 71 * is specified in terms of the destination image after transform/resize. 72 * 73 * We also offer a "force to grayscale" option, which simply discards the 74 * chrominance channels of a YCbCr image. This is lossless in the sense that 75 * the luminance channel is preserved exactly. It's not the same kind of 76 * thing as the rotate/flip transformations, but it's convenient to handle it 77 * as part of this package, mainly because the transformation routines have to 78 * be aware of the option to know how many components to work on. 79 */ 80 81 82 /* 83 * Codes for supported types of image transformations. 84 */ 85 86 typedef enum { 87 JXFORM_NONE, /* no transformation */ 88 JXFORM_FLIP_H, /* horizontal flip */ 89 JXFORM_FLIP_V, /* vertical flip */ 90 JXFORM_TRANSPOSE, /* transpose across UL-to-LR axis */ 91 JXFORM_TRANSVERSE, /* transpose across UR-to-LL axis */ 92 JXFORM_ROT_90, /* 90-degree clockwise rotation */ 93 JXFORM_ROT_180, /* 180-degree rotation */ 94 JXFORM_ROT_270 /* 270-degree clockwise (or 90 ccw) */ 95 } JXFORM_CODE; 96 97 /* 98 * Codes for crop parameters, which can individually be unspecified, 99 * positive or negative for xoffset or yoffset, 100 * positive or forced for width or height. 101 */ 102 103 typedef enum { 104 JCROP_UNSET, 105 JCROP_POS, 106 JCROP_NEG, 107 JCROP_FORCE 108 } JCROP_CODE; 109 110 /* 111 * Transform parameters struct. 112 * NB: application must not change any elements of this struct after 113 * calling jtransform_request_workspace. 114 */ 115 116 typedef struct { 117 /* Options: set by caller */ 118 JXFORM_CODE transform; /* image transform operator */ 119 boolean perfect; /* if TRUE, fail if partial MCUs are requested */ 120 boolean trim; /* if TRUE, trim partial MCUs as needed */ 121 boolean force_grayscale; /* if TRUE, convert color image to grayscale */ 122 boolean crop; /* if TRUE, crop source image */ 123 boolean slow_hflip; /* For best performance, the JXFORM_FLIP_H transform 124 normally modifies the source coefficients in place. 125 Setting this to TRUE will instead use a slower, 126 double-buffered algorithm, which leaves the source 127 coefficients in tact (necessary if other transformed 128 images must be generated from the same set of 129 coefficients. */ 130 131 /* Crop parameters: application need not set these unless crop is TRUE. 132 * These can be filled in by jtransform_parse_crop_spec(). 133 */ 134 JDIMENSION crop_width; /* Width of selected region */ 135 JCROP_CODE crop_width_set; /* (forced disables adjustment) */ 136 JDIMENSION crop_height; /* Height of selected region */ 137 JCROP_CODE crop_height_set; /* (forced disables adjustment) */ 138 JDIMENSION crop_xoffset; /* X offset of selected region */ 139 JCROP_CODE crop_xoffset_set; /* (negative measures from right edge) */ 140 JDIMENSION crop_yoffset; /* Y offset of selected region */ 141 JCROP_CODE crop_yoffset_set; /* (negative measures from bottom edge) */ 142 143 /* Internal workspace: caller should not touch these */ 144 int num_components; /* # of components in workspace */ 145 jvirt_barray_ptr * workspace_coef_arrays; /* workspace for transformations */ 146 JDIMENSION output_width; /* cropped destination dimensions */ 147 JDIMENSION output_height; 148 JDIMENSION x_crop_offset; /* destination crop offsets measured in iMCUs */ 149 JDIMENSION y_crop_offset; 150 int iMCU_sample_width; /* destination iMCU size */ 151 int iMCU_sample_height; 152 } jpeg_transform_info; 153 154 155 #if TRANSFORMS_SUPPORTED 156 157 /* Parse a crop specification (written in X11 geometry style) */ 158 EXTERN(boolean) jtransform_parse_crop_spec 159 (jpeg_transform_info *info, const char *spec); 160 /* Request any required workspace */ 161 EXTERN(boolean) jtransform_request_workspace 162 (j_decompress_ptr srcinfo, jpeg_transform_info *info); 163 /* Adjust output image parameters */ 164 EXTERN(jvirt_barray_ptr *) jtransform_adjust_parameters 165 (j_decompress_ptr srcinfo, j_compress_ptr dstinfo, 166 jvirt_barray_ptr *src_coef_arrays, jpeg_transform_info *info); 167 /* Execute the actual transformation, if any */ 168 EXTERN(void) jtransform_execute_transform 169 (j_decompress_ptr srcinfo, j_compress_ptr dstinfo, 170 jvirt_barray_ptr *src_coef_arrays, jpeg_transform_info *info); 171 /* Determine whether lossless transformation is perfectly 172 * possible for a specified image and transformation. 173 */ 174 EXTERN(boolean) jtransform_perfect_transform 175 (JDIMENSION image_width, JDIMENSION image_height, int MCU_width, 176 int MCU_height, JXFORM_CODE transform); 177 178 /* jtransform_execute_transform used to be called 179 * jtransform_execute_transformation, but some compilers complain about 180 * routine names that long. This macro is here to avoid breaking any 181 * old source code that uses the original name... 182 */ 183 #define jtransform_execute_transformation jtransform_execute_transform 184 185 #endif /* TRANSFORMS_SUPPORTED */ 186 187 188 /* 189 * Support for copying optional markers from source to destination file. 190 */ 191 192 typedef enum { 193 JCOPYOPT_NONE, /* copy no optional markers */ 194 JCOPYOPT_COMMENTS, /* copy only comment (COM) markers */ 195 JCOPYOPT_ALL /* copy all optional markers */ 196 } JCOPY_OPTION; 197 198 #define JCOPYOPT_DEFAULT JCOPYOPT_COMMENTS /* recommended default */ 199 200 /* Setup decompression object to save desired markers in memory */ 201 EXTERN(void) jcopy_markers_setup 202 (j_decompress_ptr srcinfo, JCOPY_OPTION option); 203 /* Copy markers saved in the given source object to the destination object */ 204 EXTERN(void) jcopy_markers_execute 205 (j_decompress_ptr srcinfo, j_compress_ptr dstinfo, 206 JCOPY_OPTION option); 207
