00001 /* 00002 * transupp.h 00003 * 00004 * Copyright (C) 1997, Thomas G. Lane. 00005 * This file is part of the Independent JPEG Group's software. 00006 * For conditions of distribution and use, see the accompanying README file. 00007 * 00008 * This file contains declarations for image transformation routines and 00009 * other utility code used by the jpegtran sample application. These are 00010 * NOT part of the core JPEG library. But we keep these routines separate 00011 * from jpegtran.c to ease the task of maintaining jpegtran-like programs 00012 * that have other user interfaces. 00013 * 00014 * NOTE: all the routines declared here have very specific requirements 00015 * about when they are to be executed during the reading and writing of the 00016 * source and destination files. See the comments in transupp.c, or see 00017 * jpegtran.c for an example of correct usage. 00018 */ 00019 00020 /* If you happen not to want the image transform support, disable it here */ 00021 #ifndef TRANSFORMS_SUPPORTED 00022 #define TRANSFORMS_SUPPORTED 1 /* 0 disables transform code */ 00023 #endif 00024 00025 /* Short forms of external names for systems with brain-damaged linkers. */ 00026 00027 #ifdef NEED_SHORT_EXTERNAL_NAMES 00028 #define jtransform_request_workspace jTrRequest 00029 #define jtransform_adjust_parameters jTrAdjust 00030 #define jtransform_execute_transformation jTrExec 00031 #define jcopy_markers_setup jCMrkSetup 00032 #define jcopy_markers_execute jCMrkExec 00033 #endif /* NEED_SHORT_EXTERNAL_NAMES */ 00034 00035 00036 /* 00037 * Codes for supported types of image transformations. 00038 */ 00039 00040 typedef enum { 00041 JXFORM_NONE, /* no transformation */ 00042 JXFORM_FLIP_H, /* horizontal flip */ 00043 JXFORM_FLIP_V, /* vertical flip */ 00044 JXFORM_TRANSPOSE, /* transpose across UL-to-LR axis */ 00045 JXFORM_TRANSVERSE, /* transpose across UR-to-LL axis */ 00046 JXFORM_ROT_90, /* 90-degree clockwise rotation */ 00047 JXFORM_ROT_180, /* 180-degree rotation */ 00048 JXFORM_ROT_270 /* 270-degree clockwise (or 90 ccw) */ 00049 } JXFORM_CODE; 00050 00051 /* 00052 * Although rotating and flipping data expressed as DCT coefficients is not 00053 * hard, there is an asymmetry in the JPEG format specification for images 00054 * whose dimensions aren't multiples of the iMCU size. The right and bottom 00055 * image edges are padded out to the next iMCU boundary with junk data; but 00056 * no padding is possible at the top and left edges. If we were to flip 00057 * the whole image including the pad data, then pad garbage would become 00058 * visible at the top and/or left, and real pixels would disappear into the 00059 * pad margins --- perhaps permanently, since encoders & decoders may not 00060 * bother to preserve DCT blocks that appear to be completely outside the 00061 * nominal image area. So, we have to exclude any partial iMCUs from the 00062 * basic transformation. 00063 * 00064 * Transpose is the only transformation that can handle partial iMCUs at the 00065 * right and bottom edges completely cleanly. flip_h can flip partial iMCUs 00066 * at the bottom, but leaves any partial iMCUs at the right edge untouched. 00067 * Similarly flip_v leaves any partial iMCUs at the bottom edge untouched. 00068 * The other transforms are defined as combinations of these basic transforms 00069 * and process edge blocks in a way that preserves the equivalence. 00070 * 00071 * The "trim" option causes untransformable partial iMCUs to be dropped; 00072 * this is not strictly lossless, but it usually gives the best-looking 00073 * result for odd-size images. Note that when this option is active, 00074 * the expected mathematical equivalences between the transforms may not hold. 00075 * (For example, -rot 270 -trim trims only the bottom edge, but -rot 90 -trim 00076 * followed by -rot 180 -trim trims both edges.) 00077 * 00078 * We also offer a "force to grayscale" option, which simply discards the 00079 * chrominance channels of a YCbCr image. This is lossless in the sense that 00080 * the luminance channel is preserved exactly. It's not the same kind of 00081 * thing as the rotate/flip transformations, but it's convenient to handle it 00082 * as part of this package, mainly because the transformation routines have to 00083 * be aware of the option to know how many components to work on. 00084 */ 00085 00086 typedef struct { 00087 /* Options: set by caller */ 00088 JXFORM_CODE transform; /* image transform operator */ 00089 boolean trim; /* if TRUE, trim partial MCUs as needed */ 00090 boolean force_grayscale; /* if TRUE, convert color image to grayscale */ 00091 00092 /* Internal workspace: caller should not touch these */ 00093 int num_components; /* # of components in workspace */ 00094 jvirt_barray_ptr * workspace_coef_arrays; /* workspace for transformations */ 00095 } jpeg_transform_info; 00096 00097 00098 #if TRANSFORMS_SUPPORTED 00099 00100 /* Request any required workspace */ 00101 EXTERN(void) jtransform_request_workspace 00102 JPP((j_decompress_ptr srcinfo, jpeg_transform_info *info)); 00103 /* Adjust output image parameters */ 00104 EXTERN(jvirt_barray_ptr *) jtransform_adjust_parameters 00105 JPP((j_decompress_ptr srcinfo, j_compress_ptr dstinfo, 00106 jvirt_barray_ptr *src_coef_arrays, 00107 jpeg_transform_info *info)); 00108 /* Execute the actual transformation, if any */ 00109 EXTERN(void) jtransform_execute_transformation 00110 JPP((j_decompress_ptr srcinfo, j_compress_ptr dstinfo, 00111 jvirt_barray_ptr *src_coef_arrays, 00112 jpeg_transform_info *info)); 00113 00114 #endif /* TRANSFORMS_SUPPORTED */ 00115 00116 00117 /* 00118 * Support for copying optional markers from source to destination file. 00119 */ 00120 00121 typedef enum { 00122 JCOPYOPT_NONE, /* copy no optional markers */ 00123 JCOPYOPT_COMMENTS, /* copy only comment (COM) markers */ 00124 JCOPYOPT_ALL /* copy all optional markers */ 00125 } JCOPY_OPTION; 00126 00127 #define JCOPYOPT_DEFAULT JCOPYOPT_COMMENTS /* recommended default */ 00128 00129 /* Setup decompression object to save desired markers in memory */ 00130 EXTERN(void) jcopy_markers_setup 00131 JPP((j_decompress_ptr srcinfo, JCOPY_OPTION option)); 00132 /* Copy markers saved in the given source object to the destination object */ 00133 EXTERN(void) jcopy_markers_execute 00134 JPP((j_decompress_ptr srcinfo, j_compress_ptr dstinfo, 00135 JCOPY_OPTION option));