/* | |
* transupp.h | |
* | |
* Copyright (C) 1997, Thomas G. Lane. | |
* 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 | |
/* Short forms of external names for systems with brain-damaged linkers. */ | |
#ifdef NEED_SHORT_EXTERNAL_NAMES | |
#define jtransform_request_workspace jTrRequest | |
#define jtransform_adjust_parameters jTrAdjust | |
#define jtransform_execute_transformation jTrExec | |
#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; | |
/* | |
* 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 "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. | |
*/ | |
typedef struct { | |
/* Options: set by caller */ | |
JXFORM_CODE transform; /* image transform operator */ | |
boolean trim; /* if TRUE, trim partial MCUs as needed */ | |
boolean force_grayscale; /* if TRUE, convert color image to grayscale */ | |
/* Internal workspace: caller should not touch these */ | |
int num_components; /* # of components in workspace */ | |
jvirt_barray_ptr * workspace_coef_arrays; /* workspace for transformations */ | |
} jpeg_transform_info; | |
#if TRANSFORMS_SUPPORTED | |
/* Request any required workspace */ | |
EXTERN(void) 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_transformation | |
JPP((j_decompress_ptr srcinfo, j_compress_ptr dstinfo, | |
jvirt_barray_ptr *src_coef_arrays, | |
jpeg_transform_info *info)); | |
#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)); |