1 /* 2 * transupp.h 3 * 4 * Copyright (C) 1997-2009, 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 JPEG format: the upper 55 * left corner of the selected region must fall on an iMCU boundary. If this 56 * does not hold for the given crop parameters, we silently move the upper left 57 * corner up and/or left to make it so, simultaneously increasing the region 58 * 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 * 61 * We also provide a lossless-resize option, which is kind of a lossless-crop 62 * operation in the DCT coefficient block domain - it discards higher-order 63 * coefficients and losslessly preserves lower-order coefficients of a 64 * sub-block. 65 * 66 * Rotate/flip transform, resize, and crop can be requested together in a 67 * single invocation. The crop is applied last --- that is, the crop region 68 * is specified in terms of the destination image after transform/resize. 69 * 70 * We also offer a "force to grayscale" option, which simply discards the 71 * chrominance channels of a YCbCr image. This is lossless in the sense that 72 * the luminance channel is preserved exactly. It's not the same kind of 73 * thing as the rotate/flip transformations, but it's convenient to handle it 74 * as part of this package, mainly because the transformation routines have to 75 * be aware of the option to know how many components to work on. 76 */ 77 78 79 /* Short forms of external names for systems with brain-damaged linkers. */ 80 81 #ifdef NEED_SHORT_EXTERNAL_NAMES 82 #define jtransform_parse_crop_spec jTrParCrop 83 #define jtransform_request_workspace jTrRequest 84 #define jtransform_adjust_parameters jTrAdjust 85 #define jtransform_execute_transform jTrExec 86 #define jtransform_perfect_transform jTrPerfect 87 #define jcopy_markers_setup jCMrkSetup 88 #define jcopy_markers_execute jCMrkExec 89 #endif /* NEED_SHORT_EXTERNAL_NAMES */ 90 91 92 /* 93 * Codes for supported types of image transformations. 94 */ 95 96 typedef enum { 97 JXFORM_NONE, /* no transformation */ 98 JXFORM_FLIP_H, /* horizontal flip */ 99 JXFORM_FLIP_V, /* vertical flip */ 100 JXFORM_TRANSPOSE, /* transpose across UL-to-LR axis */ 101 JXFORM_TRANSVERSE, /* transpose across UR-to-LL axis */ 102 JXFORM_ROT_90, /* 90-degree clockwise rotation */ 103 JXFORM_ROT_180, /* 180-degree rotation */ 104 JXFORM_ROT_270 /* 270-degree clockwise (or 90 ccw) */ 105 } JXFORM_CODE; 106 107 /* 108 * Codes for crop parameters, which can individually be unspecified, 109 * positive, or negative. (Negative width or height makes no sense, though.) 110 */ 111 112 typedef enum { 113 JCROP_UNSET, 114 JCROP_POS, 115 JCROP_NEG 116 } JCROP_CODE; 117 118 /* 119 * Transform parameters struct. 120 * NB: application must not change any elements of this struct after 121 * calling jtransform_request_workspace. 122 */ 123 124 typedef struct { 125 /* Options: set by caller */ 126 JXFORM_CODE transform; /* image transform operator */ 127 boolean perfect; /* if TRUE, fail if partial MCUs are requested */ 128 boolean trim; /* if TRUE, trim partial MCUs as needed */ 129 boolean force_grayscale; /* if TRUE, convert color image to grayscale */ 130 boolean crop; /* if TRUE, crop source image */ 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; 137 JDIMENSION crop_height; /* Height of selected region */ 138 JCROP_CODE crop_height_set; 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 JPP((jpeg_transform_info *info, const char *spec)); 161 /* Request any required workspace */ 162 EXTERN(boolean) jtransform_request_workspace 163 JPP((j_decompress_ptr srcinfo, jpeg_transform_info *info)); 164 /* Adjust output image parameters */ 165 EXTERN(jvirt_barray_ptr *) jtransform_adjust_parameters 166 JPP((j_decompress_ptr srcinfo, j_compress_ptr dstinfo, 167 jvirt_barray_ptr *src_coef_arrays, 168 jpeg_transform_info *info)); 169 /* Execute the actual transformation, if any */ 170 EXTERN(void) jtransform_execute_transform 171 JPP((j_decompress_ptr srcinfo, j_compress_ptr dstinfo, 172 jvirt_barray_ptr *src_coef_arrays, 173 jpeg_transform_info *info)); 174 /* Determine whether lossless transformation is perfectly 175 * possible for a specified image and transformation. 176 */ 177 EXTERN(boolean) jtransform_perfect_transform 178 JPP((JDIMENSION image_width, JDIMENSION image_height, 179 int MCU_width, int MCU_height, 180 JXFORM_CODE transform)); 181 182 /* jtransform_execute_transform used to be called 183 * jtransform_execute_transformation, but some compilers complain about 184 * routine names that long. This macro is here to avoid breaking any 185 * old source code that uses the original name... 186 */ 187 #define jtransform_execute_transformation jtransform_execute_transform 188 189 #endif /* TRANSFORMS_SUPPORTED */ 190 191 192 /* 193 * Support for copying optional markers from source to destination file. 194 */ 195 196 typedef enum { 197 JCOPYOPT_NONE, /* copy no optional markers */ 198 JCOPYOPT_COMMENTS, /* copy only comment (COM) markers */ 199 JCOPYOPT_ALL /* copy all optional markers */ 200 } JCOPY_OPTION; 201 202 #define JCOPYOPT_DEFAULT JCOPYOPT_COMMENTS /* recommended default */ 203 204 /* Setup decompression object to save desired markers in memory */ 205 EXTERN(void) jcopy_markers_setup 206 JPP((j_decompress_ptr srcinfo, JCOPY_OPTION option)); 207 /* Copy markers saved in the given source object to the destination object */ 208 EXTERN(void) jcopy_markers_execute 209 JPP((j_decompress_ptr srcinfo, j_compress_ptr dstinfo, 210 JCOPY_OPTION option)); 211