1 /* 2 * transupp.h 3 * 4 * Copyright (C) 1997-2001, Thomas G. Lane. 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 * If both crop and a rotate/flip transform are requested, the crop is applied 62 * last --- that is, the crop region is specified in terms of the destination 63 * image. 64 * 65 * We also offer a "force to grayscale" option, which simply discards the 66 * chrominance channels of a YCbCr image. This is lossless in the sense that 67 * the luminance channel is preserved exactly. It's not the same kind of 68 * thing as the rotate/flip transformations, but it's convenient to handle it 69 * as part of this package, mainly because the transformation routines have to 70 * be aware of the option to know how many components to work on. 71 */ 72 73 74 /* Short forms of external names for systems with brain-damaged linkers. */ 75 76 #ifdef NEED_SHORT_EXTERNAL_NAMES 77 #define jtransform_parse_crop_spec jTrParCrop 78 #define jtransform_request_workspace jTrRequest 79 #define jtransform_adjust_parameters jTrAdjust 80 #define jtransform_execute_transform jTrExec 81 #define jtransform_perfect_transform jTrPerfect 82 #define jcopy_markers_setup jCMrkSetup 83 #define jcopy_markers_execute jCMrkExec 84 #endif /* NEED_SHORT_EXTERNAL_NAMES */ 85 86 87 /* 88 * Codes for supported types of image transformations. 89 */ 90 91 typedef enum { 92 JXFORM_NONE, /* no transformation */ 93 JXFORM_FLIP_H, /* horizontal flip */ 94 JXFORM_FLIP_V, /* vertical flip */ 95 JXFORM_TRANSPOSE, /* transpose across UL-to-LR axis */ 96 JXFORM_TRANSVERSE, /* transpose across UR-to-LL axis */ 97 JXFORM_ROT_90, /* 90-degree clockwise rotation */ 98 JXFORM_ROT_180, /* 180-degree rotation */ 99 JXFORM_ROT_270 /* 270-degree clockwise (or 90 ccw) */ 100 } JXFORM_CODE; 101 102 /* 103 * Codes for crop parameters, which can individually be unspecified, 104 * positive, or negative. (Negative width or height makes no sense, though.) 105 */ 106 107 typedef enum { 108 JCROP_UNSET, 109 JCROP_POS, 110 JCROP_NEG 111 } JCROP_CODE; 112 113 /* 114 * Transform parameters struct. 115 * NB: application must not change any elements of this struct after 116 * calling jtransform_request_workspace. 117 */ 118 119 typedef struct { 120 /* Options: set by caller */ 121 JXFORM_CODE transform; /* image transform operator */ 122 boolean perfect; /* if TRUE, fail if partial MCUs are requested */ 123 boolean trim; /* if TRUE, trim partial MCUs as needed */ 124 boolean force_grayscale; /* if TRUE, convert color image to grayscale */ 125 boolean crop; /* if TRUE, crop source image */ 126 127 /* Crop parameters: application need not set these unless crop is TRUE. 128 * These can be filled in by jtransform_parse_crop_spec(). 129 */ 130 JDIMENSION crop_width; /* Width of selected region */ 131 JCROP_CODE crop_width_set; 132 JDIMENSION crop_height; /* Height of selected region */ 133 JCROP_CODE crop_height_set; 134 JDIMENSION crop_xoffset; /* X offset of selected region */ 135 JCROP_CODE crop_xoffset_set; /* (negative measures from right edge) */ 136 JDIMENSION crop_yoffset; /* Y offset of selected region */ 137 JCROP_CODE crop_yoffset_set; /* (negative measures from bottom edge) */ 138 139 /* Internal workspace: caller should not touch these */ 140 int num_components; /* # of components in workspace */ 141 jvirt_barray_ptr * workspace_coef_arrays; /* workspace for transformations */ 142 JDIMENSION output_width; /* cropped destination dimensions */ 143 JDIMENSION output_height; 144 JDIMENSION x_crop_offset; /* destination crop offsets measured in iMCUs */ 145 JDIMENSION y_crop_offset; 146 int max_h_samp_factor; /* destination iMCU size */ 147 int max_v_samp_factor; 148 } jpeg_transform_info; 149 150 151 #if TRANSFORMS_SUPPORTED 152 153 /* Parse a crop specification (written in X11 geometry style) */ 154 EXTERN(boolean) jtransform_parse_crop_spec 155 JPP((jpeg_transform_info *info, const char *spec)); 156 /* Request any required workspace */ 157 EXTERN(void) jtransform_request_workspace 158 JPP((j_decompress_ptr srcinfo, jpeg_transform_info *info)); 159 /* Adjust output image parameters */ 160 EXTERN(jvirt_barray_ptr *) jtransform_adjust_parameters 161 JPP((j_decompress_ptr srcinfo, j_compress_ptr dstinfo, 162 jvirt_barray_ptr *src_coef_arrays, 163 jpeg_transform_info *info)); 164 /* Execute the actual transformation, if any */ 165 EXTERN(void) jtransform_execute_transform 166 JPP((j_decompress_ptr srcinfo, j_compress_ptr dstinfo, 167 jvirt_barray_ptr *src_coef_arrays, 168 jpeg_transform_info *info)); 169 /* Determine whether lossless transformation is perfectly 170 * possible for a specified image and transformation. 171 */ 172 EXTERN(boolean) jtransform_perfect_transform 173 JPP((JDIMENSION image_width, JDIMENSION image_height, 174 int MCU_width, int MCU_height, 175 JXFORM_CODE transform)); 176 177 /* jtransform_execute_transform used to be called 178 * jtransform_execute_transformation, but some compilers complain about 179 * routine names that long. This macro is here to avoid breaking any 180 * old source code that uses the original name... 181 */ 182 #define jtransform_execute_transformation jtransform_execute_transform 183 184 #endif /* TRANSFORMS_SUPPORTED */ 185 186 187 /* 188 * Support for copying optional markers from source to destination file. 189 */ 190 191 typedef enum { 192 JCOPYOPT_NONE, /* copy no optional markers */ 193 JCOPYOPT_COMMENTS, /* copy only comment (COM) markers */ 194 JCOPYOPT_ALL /* copy all optional markers */ 195 } JCOPY_OPTION; 196 197 #define JCOPYOPT_DEFAULT JCOPYOPT_COMMENTS /* recommended default */ 198 199 /* Setup decompression object to save desired markers in memory */ 200 EXTERN(void) jcopy_markers_setup 201 JPP((j_decompress_ptr srcinfo, JCOPY_OPTION option)); 202 /* Copy markers saved in the given source object to the destination object */ 203 EXTERN(void) jcopy_markers_execute 204 JPP((j_decompress_ptr srcinfo, j_compress_ptr dstinfo, 205 JCOPY_OPTION option)); 206