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Diffstat (limited to 'jpg/transupp.h')
| -rw-r--r-- | jpg/transupp.h | 213 |
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diff --git a/jpg/transupp.h b/jpg/transupp.h new file mode 100644 index 0000000..9aa0af3 --- /dev/null +++ b/jpg/transupp.h @@ -0,0 +1,213 @@ +/* + * transupp.h + * + * Copyright (C) 1997-2011, Thomas G. Lane, Guido Vollbeding. + * This file is part of the Independent JPEG Group's software. + * For conditions of distribution and use, see the accompanying README file. + * + * This file contains declarations for image transformation routines and + * other utility code used by the jpegtran sample application. These are + * NOT part of the core JPEG library. But we keep these routines separate + * from jpegtran.c to ease the task of maintaining jpegtran-like programs + * that have other user interfaces. + * + * NOTE: all the routines declared here have very specific requirements + * about when they are to be executed during the reading and writing of the + * source and destination files. See the comments in transupp.c, or see + * jpegtran.c for an example of correct usage. + */ + +/* If you happen not to want the image transform support, disable it here */ +#ifndef TRANSFORMS_SUPPORTED +#define TRANSFORMS_SUPPORTED 1 /* 0 disables transform code */ +#endif + +/* + * Although rotating and flipping data expressed as DCT coefficients is not + * hard, there is an asymmetry in the JPEG format specification for images + * whose dimensions aren't multiples of the iMCU size. The right and bottom + * image edges are padded out to the next iMCU boundary with junk data; but + * no padding is possible at the top and left edges. If we were to flip + * the whole image including the pad data, then pad garbage would become + * visible at the top and/or left, and real pixels would disappear into the + * pad margins --- perhaps permanently, since encoders & decoders may not + * bother to preserve DCT blocks that appear to be completely outside the + * nominal image area. So, we have to exclude any partial iMCUs from the + * basic transformation. + * + * Transpose is the only transformation that can handle partial iMCUs at the + * right and bottom edges completely cleanly. flip_h can flip partial iMCUs + * at the bottom, but leaves any partial iMCUs at the right edge untouched. + * Similarly flip_v leaves any partial iMCUs at the bottom edge untouched. + * The other transforms are defined as combinations of these basic transforms + * and process edge blocks in a way that preserves the equivalence. + * + * The "trim" option causes untransformable partial iMCUs to be dropped; + * this is not strictly lossless, but it usually gives the best-looking + * result for odd-size images. Note that when this option is active, + * the expected mathematical equivalences between the transforms may not hold. + * (For example, -rot 270 -trim trims only the bottom edge, but -rot 90 -trim + * followed by -rot 180 -trim trims both edges.) + * + * We also offer a lossless-crop option, which discards data outside a given + * image region but losslessly preserves what is inside. Like the rotate and + * flip transforms, lossless crop is restricted by the JPEG format: the upper + * left corner of the selected region must fall on an iMCU boundary. If this + * does not hold for the given crop parameters, we silently move the upper left + * corner up and/or left to make it so, simultaneously increasing the region + * dimensions to keep the lower right crop corner unchanged. (Thus, the + * output image covers at least the requested region, but may cover more.) + * The adjustment of the region dimensions may be optionally disabled. + * + * We also provide a lossless-resize option, which is kind of a lossless-crop + * operation in the DCT coefficient block domain - it discards higher-order + * coefficients and losslessly preserves lower-order coefficients of a + * sub-block. + * + * Rotate/flip transform, resize, and crop can be requested together in a + * single invocation. The crop is applied last --- that is, the crop region + * is specified in terms of the destination image after transform/resize. + * + * We also offer a "force to grayscale" option, which simply discards the + * chrominance channels of a YCbCr image. This is lossless in the sense that + * the luminance channel is preserved exactly. It's not the same kind of + * thing as the rotate/flip transformations, but it's convenient to handle it + * as part of this package, mainly because the transformation routines have to + * be aware of the option to know how many components to work on. + */ + + +/* Short forms of external names for systems with brain-damaged linkers. */ + +#ifdef NEED_SHORT_EXTERNAL_NAMES +#define jtransform_parse_crop_spec jTrParCrop +#define jtransform_request_workspace jTrRequest +#define jtransform_adjust_parameters jTrAdjust +#define jtransform_execute_transform jTrExec +#define jtransform_perfect_transform jTrPerfect +#define jcopy_markers_setup jCMrkSetup +#define jcopy_markers_execute jCMrkExec +#endif /* NEED_SHORT_EXTERNAL_NAMES */ + + +/* + * Codes for supported types of image transformations. + */ + +typedef enum { + JXFORM_NONE, /* no transformation */ + JXFORM_FLIP_H, /* horizontal flip */ + JXFORM_FLIP_V, /* vertical flip */ + JXFORM_TRANSPOSE, /* transpose across UL-to-LR axis */ + JXFORM_TRANSVERSE, /* transpose across UR-to-LL axis */ + JXFORM_ROT_90, /* 90-degree clockwise rotation */ + JXFORM_ROT_180, /* 180-degree rotation */ + JXFORM_ROT_270 /* 270-degree clockwise (or 90 ccw) */ +} JXFORM_CODE; + +/* + * Codes for crop parameters, which can individually be unspecified, + * positive or negative for xoffset or yoffset, + * positive or forced for width or height. + */ + +typedef enum { + JCROP_UNSET, + JCROP_POS, + JCROP_NEG, + JCROP_FORCE +} JCROP_CODE; + +/* + * Transform parameters struct. + * NB: application must not change any elements of this struct after + * calling jtransform_request_workspace. + */ + +typedef struct { + /* Options: set by caller */ + JXFORM_CODE transform; /* image transform operator */ + boolean perfect; /* if TRUE, fail if partial MCUs are requested */ + boolean trim; /* if TRUE, trim partial MCUs as needed */ + boolean force_grayscale; /* if TRUE, convert color image to grayscale */ + boolean crop; /* if TRUE, crop source image */ + + /* Crop parameters: application need not set these unless crop is TRUE. + * These can be filled in by jtransform_parse_crop_spec(). + */ + JDIMENSION crop_width; /* Width of selected region */ + JCROP_CODE crop_width_set; /* (forced disables adjustment) */ + JDIMENSION crop_height; /* Height of selected region */ + JCROP_CODE crop_height_set; /* (forced disables adjustment) */ + JDIMENSION crop_xoffset; /* X offset of selected region */ + JCROP_CODE crop_xoffset_set; /* (negative measures from right edge) */ + JDIMENSION crop_yoffset; /* Y offset of selected region */ + JCROP_CODE crop_yoffset_set; /* (negative measures from bottom edge) */ + + /* Internal workspace: caller should not touch these */ + int num_components; /* # of components in workspace */ + jvirt_barray_ptr * workspace_coef_arrays; /* workspace for transformations */ + JDIMENSION output_width; /* cropped destination dimensions */ + JDIMENSION output_height; + JDIMENSION x_crop_offset; /* destination crop offsets measured in iMCUs */ + JDIMENSION y_crop_offset; + int iMCU_sample_width; /* destination iMCU size */ + int iMCU_sample_height; +} jpeg_transform_info; + + +#if TRANSFORMS_SUPPORTED + +/* Parse a crop specification (written in X11 geometry style) */ +EXTERN(boolean) jtransform_parse_crop_spec + JPP((jpeg_transform_info *info, const char *spec)); +/* Request any required workspace */ +EXTERN(boolean) jtransform_request_workspace + JPP((j_decompress_ptr srcinfo, jpeg_transform_info *info)); +/* Adjust output image parameters */ +EXTERN(jvirt_barray_ptr *) jtransform_adjust_parameters + JPP((j_decompress_ptr srcinfo, j_compress_ptr dstinfo, + jvirt_barray_ptr *src_coef_arrays, + jpeg_transform_info *info)); +/* Execute the actual transformation, if any */ +EXTERN(void) jtransform_execute_transform + JPP((j_decompress_ptr srcinfo, j_compress_ptr dstinfo, + jvirt_barray_ptr *src_coef_arrays, + jpeg_transform_info *info)); +/* Determine whether lossless transformation is perfectly + * possible for a specified image and transformation. + */ +EXTERN(boolean) jtransform_perfect_transform + JPP((JDIMENSION image_width, JDIMENSION image_height, + int MCU_width, int MCU_height, + JXFORM_CODE transform)); + +/* jtransform_execute_transform used to be called + * jtransform_execute_transformation, but some compilers complain about + * routine names that long. This macro is here to avoid breaking any + * old source code that uses the original name... + */ +#define jtransform_execute_transformation jtransform_execute_transform + +#endif /* TRANSFORMS_SUPPORTED */ + + +/* + * Support for copying optional markers from source to destination file. + */ + +typedef enum { + JCOPYOPT_NONE, /* copy no optional markers */ + JCOPYOPT_COMMENTS, /* copy only comment (COM) markers */ + JCOPYOPT_ALL /* copy all optional markers */ +} JCOPY_OPTION; + +#define JCOPYOPT_DEFAULT JCOPYOPT_COMMENTS /* recommended default */ + +/* Setup decompression object to save desired markers in memory */ +EXTERN(void) jcopy_markers_setup + JPP((j_decompress_ptr srcinfo, JCOPY_OPTION option)); +/* Copy markers saved in the given source object to the destination object */ +EXTERN(void) jcopy_markers_execute + JPP((j_decompress_ptr srcinfo, j_compress_ptr dstinfo, + JCOPY_OPTION option)); |