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.ijg 9 * file. 10 * 11 * This file contains declarations for image transformation routines and 12 * other utility code used by the jpegtran sample application. These are 13 * NOT part of the core JPEG library. But we keep these routines separate 14 * from jpegtran.c to ease the task of maintaining jpegtran-like programs 15 * that have other user interfaces. 16 * 17 * NOTE: all the routines declared here have very specific requirements 18 * about when they are to be executed during the reading and writing of the 19 * source and destination files. See the comments in transupp.c, or see 20 * jpegtran.c for an example of correct usage. 21 */ 22 23 /* If you happen not to want the image transform support, disable it here */ 24 #ifndef TRANSFORMS_SUPPORTED 25 #define TRANSFORMS_SUPPORTED 1 /* 0 disables transform code */ 26 #endif 27 28 /* 29 * Although rotating and flipping data expressed as DCT coefficients is not 30 * hard, there is an asymmetry in the JPEG format specification for images 31 * whose dimensions aren't multiples of the iMCU size. The right and bottom 32 * image edges are padded out to the next iMCU boundary with junk data; but 33 * no padding is possible at the top and left edges. If we were to flip 34 * the whole image including the pad data, then pad garbage would become 35 * visible at the top and/or left, and real pixels would disappear into the 36 * pad margins --- perhaps permanently, since encoders & decoders may not 37 * bother to preserve DCT blocks that appear to be completely outside the 38 * nominal image area. So, we have to exclude any partial iMCUs from the 39 * basic transformation. 40 * 41 * Transpose is the only transformation that can handle partial iMCUs at the 42 * right and bottom edges completely cleanly. flip_h can flip partial iMCUs 43 * at the bottom, but leaves any partial iMCUs at the right edge untouched. 44 * Similarly flip_v leaves any partial iMCUs at the bottom edge untouched. 45 * The other transforms are defined as combinations of these basic transforms 46 * and process edge blocks in a way that preserves the equivalence. 47 * 48 * The "trim" option causes untransformable partial iMCUs to be dropped; 49 * this is not strictly lossless, but it usually gives the best-looking 50 * result for odd-size images. Note that when this option is active, 51 * the expected mathematical equivalences between the transforms may not hold. 52 * (For example, -rot 270 -trim trims only the bottom edge, but -rot 90 -trim 53 * followed by -rot 180 -trim trims both edges.) 54 * 55 * We also offer a lossless-crop option, which discards data outside a given 56 * image region but losslessly preserves what is inside. Like the rotate and 57 * flip transforms, lossless crop is restricted by the JPEG format: the upper 58 * left corner of the selected region must fall on an iMCU boundary. If this 59 * does not hold for the given crop parameters, we silently move the upper left 60 * corner up and/or left to make it so, simultaneously increasing the region 61 * dimensions to keep the lower right crop corner unchanged. (Thus, the 62 * output image covers at least the requested region, but may cover more.) 63 * The adjustment of the region dimensions may be optionally disabled. 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 /* 84 * Codes for supported types of image transformations. 85 */ 86 87 typedef enum { 88 JXFORM_NONE, /* no transformation */ 89 JXFORM_FLIP_H, /* horizontal flip */ 90 JXFORM_FLIP_V, /* vertical flip */ 91 JXFORM_TRANSPOSE, /* transpose across UL-to-LR axis */ 92 JXFORM_TRANSVERSE, /* transpose across UR-to-LL axis */ 93 JXFORM_ROT_90, /* 90-degree clockwise rotation */ 94 JXFORM_ROT_180, /* 180-degree rotation */ 95 JXFORM_ROT_270 /* 270-degree clockwise (or 90 ccw) */ 96 } JXFORM_CODE; 97 98 /* 99 * Codes for crop parameters, which can individually be unspecified, 100 * positive or negative for xoffset or yoffset, 101 * positive or forced for width or height. 102 */ 103 104 typedef enum { 105 JCROP_UNSET, 106 JCROP_POS, 107 JCROP_NEG, 108 JCROP_FORCE 109 } JCROP_CODE; 110 111 /* 112 * Transform parameters struct. 113 * NB: application must not change any elements of this struct after 114 * calling jtransform_request_workspace. 115 */ 116 117 typedef struct { 118 /* Options: set by caller */ 119 JXFORM_CODE transform; /* image transform operator */ 120 boolean perfect; /* if TRUE, fail if partial MCUs are requested */ 121 boolean trim; /* if TRUE, trim partial MCUs as needed */ 122 boolean force_grayscale; /* if TRUE, convert color image to grayscale */ 123 boolean crop; /* if TRUE, crop source image */ 124 boolean slow_hflip; /* For best performance, the JXFORM_FLIP_H transform 125 normally modifies the source coefficients in place. 126 Setting this to TRUE will instead use a slower, 127 double-buffered algorithm, which leaves the source 128 coefficients in tact (necessary if other transformed 129 images must be generated from the same set of 130 coefficients. */ 131 132 /* Crop parameters: application need not set these unless crop is TRUE. 133 * These can be filled in by jtransform_parse_crop_spec(). 134 */ 135 JDIMENSION crop_width; /* Width of selected region */ 136 JCROP_CODE crop_width_set; /* (forced disables adjustment) */ 137 JDIMENSION crop_height; /* Height of selected region */ 138 JCROP_CODE crop_height_set; /* (forced disables adjustment) */ 139 JDIMENSION crop_xoffset; /* X offset of selected region */ 140 JCROP_CODE crop_xoffset_set; /* (negative measures from right edge) */ 141 JDIMENSION crop_yoffset; /* Y offset of selected region */ 142 JCROP_CODE crop_yoffset_set; /* (negative measures from bottom edge) */ 143 144 /* Internal workspace: caller should not touch these */ 145 int num_components; /* # of components in workspace */ 146 jvirt_barray_ptr *workspace_coef_arrays; /* workspace for transformations */ 147 JDIMENSION output_width; /* cropped destination dimensions */ 148 JDIMENSION output_height; 149 JDIMENSION x_crop_offset; /* destination crop offsets measured in iMCUs */ 150 JDIMENSION y_crop_offset; 151 int iMCU_sample_width; /* destination iMCU size */ 152 int iMCU_sample_height; 153 } jpeg_transform_info; 154 155 156 #if TRANSFORMS_SUPPORTED 157 158 /* Parse a crop specification (written in X11 geometry style) */ 159 EXTERN(boolean) jtransform_parse_crop_spec 160 (jpeg_transform_info *info, const char *spec); 161 /* Request any required workspace */ 162 EXTERN(boolean) jtransform_request_workspace 163 (j_decompress_ptr srcinfo, jpeg_transform_info *info); 164 /* Adjust output image parameters */ 165 EXTERN(jvirt_barray_ptr *) jtransform_adjust_parameters 166 (j_decompress_ptr srcinfo, j_compress_ptr dstinfo, 167 jvirt_barray_ptr *src_coef_arrays, jpeg_transform_info *info); 168 /* Execute the actual transformation, if any */ 169 EXTERN(void) jtransform_execute_transform 170 (j_decompress_ptr srcinfo, j_compress_ptr dstinfo, 171 jvirt_barray_ptr *src_coef_arrays, jpeg_transform_info *info); 172 /* Determine whether lossless transformation is perfectly 173 * possible for a specified image and transformation. 174 */ 175 EXTERN(boolean) jtransform_perfect_transform 176 (JDIMENSION image_width, JDIMENSION image_height, int MCU_width, 177 int MCU_height, JXFORM_CODE transform); 178 179 /* jtransform_execute_transform used to be called 180 * jtransform_execute_transformation, but some compilers complain about 181 * routine names that long. This macro is here to avoid breaking any 182 * old source code that uses the original name... 183 */ 184 #define jtransform_execute_transformation jtransform_execute_transform 185 186 #endif /* TRANSFORMS_SUPPORTED */ 187 188 189 /* 190 * Support for copying optional markers from source to destination file. 191 */ 192 193 typedef enum { 194 JCOPYOPT_NONE, /* copy no optional markers */ 195 JCOPYOPT_COMMENTS, /* copy only comment (COM) markers */ 196 JCOPYOPT_ALL /* copy all optional markers */ 197 } JCOPY_OPTION; 198 199 #define JCOPYOPT_DEFAULT JCOPYOPT_COMMENTS /* recommended default */ 200 201 /* Setup decompression object to save desired markers in memory */ 202 EXTERN(void) jcopy_markers_setup 203 (j_decompress_ptr srcinfo, JCOPY_OPTION option); 204 /* Copy markers saved in the given source object to the destination object */ 205 EXTERN(void) jcopy_markers_execute 206 (j_decompress_ptr srcinfo, j_compress_ptr dstinfo, 207 JCOPY_OPTION option); 208
