/* * transupp.h * * Copyright (C) 1997-2009, 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.) * * 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. (Negative width or height makes no sense, though.) */ typedef enum { JCROP_UNSET, JCROP_POS, JCROP_NEG } 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; JDIMENSION crop_height; /* Height of selected region */ JCROP_CODE crop_height_set; 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));
