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| 1 /* |
| 2 * transupp.h |
| 3 * |
| 4 * Copyright (C) 1997, 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 /* Short forms of external names for systems with brain-damaged linkers. */ |
| 26 |
| 27 #ifdef NEED_SHORT_EXTERNAL_NAMES |
| 28 #define jtransform_request_workspace jTrRequest |
| 29 #define jtransform_adjust_parameters jTrAdjust |
| 30 #define jtransform_execute_transformation jTrExec |
| 31 #define jcopy_markers_setup jCMrkSetup |
| 32 #define jcopy_markers_execute jCMrkExec |
| 33 #endif /* NEED_SHORT_EXTERNAL_NAMES */ |
| 34 |
| 35 |
| 36 /* |
| 37 * Codes for supported types of image transformations. |
| 38 */ |
| 39 |
| 40 typedef enum { |
| 41 JXFORM_NONE, /* no transformation */ |
| 42 JXFORM_FLIP_H, /* horizontal flip */ |
| 43 JXFORM_FLIP_V, /* vertical flip */ |
| 44 JXFORM_TRANSPOSE, /* transpose across UL-to-LR axis */ |
| 45 JXFORM_TRANSVERSE, /* transpose across UR-to-LL axis */ |
| 46 JXFORM_ROT_90, /* 90-degree clockwise rotation */ |
| 47 JXFORM_ROT_180, /* 180-degree rotation */ |
| 48 JXFORM_ROT_270 /* 270-degree clockwise (or 90 ccw) */ |
| 49 } JXFORM_CODE; |
| 50 |
| 51 /* |
| 52 * Although rotating and flipping data expressed as DCT coefficients is not |
| 53 * hard, there is an asymmetry in the JPEG format specification for images |
| 54 * whose dimensions aren't multiples of the iMCU size. The right and bottom |
| 55 * image edges are padded out to the next iMCU boundary with junk data; but |
| 56 * no padding is possible at the top and left edges. If we were to flip |
| 57 * the whole image including the pad data, then pad garbage would become |
| 58 * visible at the top and/or left, and real pixels would disappear into the |
| 59 * pad margins --- perhaps permanently, since encoders & decoders may not |
| 60 * bother to preserve DCT blocks that appear to be completely outside the |
| 61 * nominal image area. So, we have to exclude any partial iMCUs from the |
| 62 * basic transformation. |
| 63 * |
| 64 * Transpose is the only transformation that can handle partial iMCUs at the |
| 65 * right and bottom edges completely cleanly. flip_h can flip partial iMCUs |
| 66 * at the bottom, but leaves any partial iMCUs at the right edge untouched. |
| 67 * Similarly flip_v leaves any partial iMCUs at the bottom edge untouched. |
| 68 * The other transforms are defined as combinations of these basic transforms |
| 69 * and process edge blocks in a way that preserves the equivalence. |
| 70 * |
| 71 * The "trim" option causes untransformable partial iMCUs to be dropped; |
| 72 * this is not strictly lossless, but it usually gives the best-looking |
| 73 * result for odd-size images. Note that when this option is active, |
| 74 * the expected mathematical equivalences between the transforms may not hold. |
| 75 * (For example, -rot 270 -trim trims only the bottom edge, but -rot 90 -trim |
| 76 * followed by -rot 180 -trim trims both edges.) |
| 77 * |
| 78 * We also offer a "force to grayscale" option, which simply discards the |
| 79 * chrominance channels of a YCbCr image. This is lossless in the sense that |
| 80 * the luminance channel is preserved exactly. It's not the same kind of |
| 81 * thing as the rotate/flip transformations, but it's convenient to handle it |
| 82 * as part of this package, mainly because the transformation routines have to |
| 83 * be aware of the option to know how many components to work on. |
| 84 */ |
| 85 |
| 86 typedef struct { |
| 87 /* Options: set by caller */ |
| 88 JXFORM_CODE transform; /* image transform operator */ |
| 89 boolean trim; /* if TRUE, trim partial MCUs as needed */ |
| 90 boolean force_grayscale; /* if TRUE, convert color image to grayscale */ |
| 91 |
| 92 /* Internal workspace: caller should not touch these */ |
| 93 int num_components; /* # of components in workspace */ |
| 94 jvirt_barray_ptr * workspace_coef_arrays; /* workspace for transformations */ |
| 95 } jpeg_transform_info; |
| 96 |
| 97 |
| 98 #if TRANSFORMS_SUPPORTED |
| 99 |
| 100 /* Request any required workspace */ |
| 101 EXTERN(void) jtransform_request_workspace |
| 102 JPP((j_decompress_ptr srcinfo, jpeg_transform_info *info)); |
| 103 /* Adjust output image parameters */ |
| 104 EXTERN(jvirt_barray_ptr *) jtransform_adjust_parameters |
| 105 JPP((j_decompress_ptr srcinfo, j_compress_ptr dstinfo, |
| 106 jvirt_barray_ptr *src_coef_arrays, |
| 107 jpeg_transform_info *info)); |
| 108 /* Execute the actual transformation, if any */ |
| 109 EXTERN(void) jtransform_execute_transformation |
| 110 JPP((j_decompress_ptr srcinfo, j_compress_ptr dstinfo, |
| 111 jvirt_barray_ptr *src_coef_arrays, |
| 112 jpeg_transform_info *info)); |
| 113 |
| 114 #endif /* TRANSFORMS_SUPPORTED */ |
| 115 |
| 116 |
| 117 /* |
| 118 * Support for copying optional markers from source to destination file. |
| 119 */ |
| 120 |
| 121 typedef enum { |
| 122 JCOPYOPT_NONE, /* copy no optional markers */ |
| 123 JCOPYOPT_COMMENTS, /* copy only comment (COM) markers */ |
| 124 JCOPYOPT_ALL /* copy all optional markers */ |
| 125 } JCOPY_OPTION; |
| 126 |
| 127 #define JCOPYOPT_DEFAULT JCOPYOPT_COMMENTS /* recommended default */ |
| 128 |
| 129 /* Setup decompression object to save desired markers in memory */ |
| 130 EXTERN(void) jcopy_markers_setup |
| 131 JPP((j_decompress_ptr srcinfo, JCOPY_OPTION option)); |
| 132 /* Copy markers saved in the given source object to the destination object */ |
| 133 EXTERN(void) jcopy_markers_execute |
| 134 JPP((j_decompress_ptr srcinfo, j_compress_ptr dstinfo, |
| 135 JCOPY_OPTION option)); |
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