1 /* 2 * transupp.h 3 * 4 * This file was part of the Independent JPEG Group's software: 5 * Copyright (C) 1997-2019, Thomas G. Lane, Guido Vollbeding. 6 * libjpeg-turbo Modifications: 7 * Copyright (C) 2017, 2021, D. R. Commander. 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 * A complementary lossless wipe option is provided to discard (gray out) data 66 * inside a given image region while losslessly preserving what is outside. 67 * A lossless drop option is also provided, which allows another JPEG image to 68 * be inserted ("dropped") into the source image data at a given position, 69 * replacing the existing image data at that position. Both the source image 70 * and the drop image must have the same subsampling level. It is best if they 71 * also have the same quantization (quality.) Otherwise, the quantization of 72 * the output image will be adapted to accommodate the higher of the source 73 * image quality and the drop image quality. The trim option can be used with 74 * the drop option to requantize the drop image to match the source image. 75 * 76 * We also provide a lossless-resize option, which is kind of a lossless-crop 77 * operation in the DCT coefficient block domain - it discards higher-order 78 * coefficients and losslessly preserves lower-order coefficients of a 79 * sub-block. 80 * 81 * Rotate/flip transform, resize, and crop can be requested together in a 82 * single invocation. The crop is applied last --- that is, the crop region 83 * is specified in terms of the destination image after transform/resize. 84 * 85 * We also offer a "force to grayscale" option, which simply discards the 86 * chrominance channels of a YCbCr image. This is lossless in the sense that 87 * the luminance channel is preserved exactly. It's not the same kind of 88 * thing as the rotate/flip transformations, but it's convenient to handle it 89 * as part of this package, mainly because the transformation routines have to 90 * be aware of the option to know how many components to work on. 91 */ 92 93 94 /* 95 * Codes for supported types of image transformations. 96 */ 97 98 typedef enum { 99 JXFORM_NONE, /* no transformation */ 100 JXFORM_FLIP_H, /* horizontal flip */ 101 JXFORM_FLIP_V, /* vertical flip */ 102 JXFORM_TRANSPOSE, /* transpose across UL-to-LR axis */ 103 JXFORM_TRANSVERSE, /* transpose across UR-to-LL axis */ 104 JXFORM_ROT_90, /* 90-degree clockwise rotation */ 105 JXFORM_ROT_180, /* 180-degree rotation */ 106 JXFORM_ROT_270, /* 270-degree clockwise (or 90 ccw) */ 107 JXFORM_WIPE, /* wipe */ 108 JXFORM_DROP /* drop */ 109 } JXFORM_CODE; 110 111 /* 112 * Codes for crop parameters, which can individually be unspecified, 113 * positive or negative for xoffset or yoffset, 114 * positive or force or reflect for width or height. 115 */ 116 117 typedef enum { 118 JCROP_UNSET, 119 JCROP_POS, 120 JCROP_NEG, 121 JCROP_FORCE, 122 JCROP_REFLECT 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, or drop */ 138 boolean slow_hflip; /* For best performance, the JXFORM_FLIP_H transform 139 normally modifies the source coefficients in place. 140 Setting this to TRUE will instead use a slower, 141 double-buffered algorithm, which leaves the source 142 coefficients in tact (necessary if other transformed 143 images must be generated from the same set of 144 coefficients. */ 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(jpeg_transform_info *info, 180 const char *spec); 181 /* Request any required workspace */ 182 EXTERN(boolean) jtransform_request_workspace(j_decompress_ptr srcinfo, 183 jpeg_transform_info *info); 184 /* Adjust output image parameters */ 185 EXTERN(jvirt_barray_ptr *) jtransform_adjust_parameters 186 (j_decompress_ptr srcinfo, j_compress_ptr dstinfo, 187 jvirt_barray_ptr *src_coef_arrays, jpeg_transform_info *info); 188 /* Execute the actual transformation, if any */ 189 EXTERN(void) jtransform_execute_transform(j_decompress_ptr srcinfo, 190 j_compress_ptr dstinfo, 191 jvirt_barray_ptr *src_coef_arrays, 192 jpeg_transform_info *info); 193 /* Determine whether lossless transformation is perfectly 194 * possible for a specified image and transformation. 195 */ 196 EXTERN(boolean) jtransform_perfect_transform(JDIMENSION image_width, 197 JDIMENSION image_height, 198 int MCU_width, int MCU_height, 199 JXFORM_CODE transform); 200 201 /* jtransform_execute_transform used to be called 202 * jtransform_execute_transformation, but some compilers complain about 203 * routine names that long. This macro is here to avoid breaking any 204 * old source code that uses the original name... 205 */ 206 #define jtransform_execute_transformation jtransform_execute_transform 207 208 #endif /* TRANSFORMS_SUPPORTED */ 209 210 211 /* 212 * Support for copying optional markers from source to destination file. 213 */ 214 215 typedef enum { 216 JCOPYOPT_NONE, /* copy no optional markers */ 217 JCOPYOPT_COMMENTS, /* copy only comment (COM) markers */ 218 JCOPYOPT_ALL, /* copy all optional markers */ 219 JCOPYOPT_ALL_EXCEPT_ICC, /* copy all optional markers except APP2 */ 220 JCOPYOPT_ICC /* copy only ICC profile (APP2) markers */ 221 } JCOPY_OPTION; 222 223 #define JCOPYOPT_DEFAULT JCOPYOPT_COMMENTS /* recommended default */ 224 225 /* Setup decompression object to save desired markers in memory */ 226 EXTERN(void) jcopy_markers_setup(j_decompress_ptr srcinfo, 227 JCOPY_OPTION option); 228 /* Copy markers saved in the given source object to the destination object */ 229 EXTERN(void) jcopy_markers_execute(j_decompress_ptr srcinfo, 230 j_compress_ptr dstinfo, 231 JCOPY_OPTION option); 232