211 lines
8.9 KiB
C
211 lines
8.9 KiB
C
/*
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* transupp.h
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*
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* Copyright (C) 1997-2009, Thomas G. Lane, Guido Vollbeding.
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* This file is part of the Independent JPEG Group's software.
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* For conditions of distribution and use, see the accompanying README file.
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*
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* This file contains declarations for image transformation routines and
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* other utility code used by the jpegtran sample application. These are
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* NOT part of the core JPEG library. But we keep these routines separate
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* from jpegtran.c to ease the task of maintaining jpegtran-like programs
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* that have other user interfaces.
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*
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* NOTE: all the routines declared here have very specific requirements
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* about when they are to be executed during the reading and writing of the
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* source and destination files. See the comments in transupp.c, or see
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* jpegtran.c for an example of correct usage.
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*/
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/* If you happen not to want the image transform support, disable it here */
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#ifndef TRANSFORMS_SUPPORTED
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#define TRANSFORMS_SUPPORTED 1 /* 0 disables transform code */
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#endif
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/*
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* Although rotating and flipping data expressed as DCT coefficients is not
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* hard, there is an asymmetry in the JPEG format specification for images
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* whose dimensions aren't multiples of the iMCU size. The right and bottom
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* image edges are padded out to the next iMCU boundary with junk data; but
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* no padding is possible at the top and left edges. If we were to flip
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* the whole image including the pad data, then pad garbage would become
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* visible at the top and/or left, and real pixels would disappear into the
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* pad margins --- perhaps permanently, since encoders & decoders may not
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* bother to preserve DCT blocks that appear to be completely outside the
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* nominal image area. So, we have to exclude any partial iMCUs from the
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* basic transformation.
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*
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* Transpose is the only transformation that can handle partial iMCUs at the
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* right and bottom edges completely cleanly. flip_h can flip partial iMCUs
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* at the bottom, but leaves any partial iMCUs at the right edge untouched.
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* Similarly flip_v leaves any partial iMCUs at the bottom edge untouched.
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* The other transforms are defined as combinations of these basic transforms
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* and process edge blocks in a way that preserves the equivalence.
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*
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* The "trim" option causes untransformable partial iMCUs to be dropped;
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* this is not strictly lossless, but it usually gives the best-looking
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* result for odd-size images. Note that when this option is active,
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* the expected mathematical equivalences between the transforms may not hold.
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* (For example, -rot 270 -trim trims only the bottom edge, but -rot 90 -trim
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* followed by -rot 180 -trim trims both edges.)
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*
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* We also offer a lossless-crop option, which discards data outside a given
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* image region but losslessly preserves what is inside. Like the rotate and
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* flip transforms, lossless crop is restricted by the JPEG format: the upper
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* left corner of the selected region must fall on an iMCU boundary. If this
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* does not hold for the given crop parameters, we silently move the upper left
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* corner up and/or left to make it so, simultaneously increasing the region
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* dimensions to keep the lower right crop corner unchanged. (Thus, the
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* output image covers at least the requested region, but may cover more.)
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*
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* We also provide a lossless-resize option, which is kind of a lossless-crop
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* operation in the DCT coefficient block domain - it discards higher-order
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* coefficients and losslessly preserves lower-order coefficients of a
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* sub-block.
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*
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* Rotate/flip transform, resize, and crop can be requested together in a
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* single invocation. The crop is applied last --- that is, the crop region
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* is specified in terms of the destination image after transform/resize.
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*
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* We also offer a "force to grayscale" option, which simply discards the
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* chrominance channels of a YCbCr image. This is lossless in the sense that
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* the luminance channel is preserved exactly. It's not the same kind of
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* thing as the rotate/flip transformations, but it's convenient to handle it
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* as part of this package, mainly because the transformation routines have to
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* be aware of the option to know how many components to work on.
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*/
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/* Short forms of external names for systems with brain-damaged linkers. */
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#ifdef NEED_SHORT_EXTERNAL_NAMES
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#define jtransform_parse_crop_spec jTrParCrop
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#define jtransform_request_workspace jTrRequest
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#define jtransform_adjust_parameters jTrAdjust
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#define jtransform_execute_transform jTrExec
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#define jtransform_perfect_transform jTrPerfect
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#define jcopy_markers_setup jCMrkSetup
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#define jcopy_markers_execute jCMrkExec
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#endif /* NEED_SHORT_EXTERNAL_NAMES */
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/*
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* Codes for supported types of image transformations.
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*/
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typedef enum {
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JXFORM_NONE, /* no transformation */
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JXFORM_FLIP_H, /* horizontal flip */
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JXFORM_FLIP_V, /* vertical flip */
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JXFORM_TRANSPOSE, /* transpose across UL-to-LR axis */
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JXFORM_TRANSVERSE, /* transpose across UR-to-LL axis */
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JXFORM_ROT_90, /* 90-degree clockwise rotation */
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JXFORM_ROT_180, /* 180-degree rotation */
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JXFORM_ROT_270 /* 270-degree clockwise (or 90 ccw) */
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} JXFORM_CODE;
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/*
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* Codes for crop parameters, which can individually be unspecified,
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* positive, or negative. (Negative width or height makes no sense, though.)
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*/
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typedef enum {
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JCROP_UNSET,
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JCROP_POS,
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JCROP_NEG
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} JCROP_CODE;
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/*
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* Transform parameters struct.
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* NB: application must not change any elements of this struct after
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* calling jtransform_request_workspace.
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*/
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typedef struct {
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/* Options: set by caller */
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JXFORM_CODE transform; /* image transform operator */
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boolean perfect; /* if TRUE, fail if partial MCUs are requested */
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boolean trim; /* if TRUE, trim partial MCUs as needed */
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boolean force_grayscale; /* if TRUE, convert color image to grayscale */
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boolean crop; /* if TRUE, crop source image */
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/* Crop parameters: application need not set these unless crop is TRUE.
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* These can be filled in by jtransform_parse_crop_spec().
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*/
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JDIMENSION crop_width; /* Width of selected region */
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JCROP_CODE crop_width_set;
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JDIMENSION crop_height; /* Height of selected region */
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JCROP_CODE crop_height_set;
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JDIMENSION crop_xoffset; /* X offset of selected region */
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JCROP_CODE crop_xoffset_set; /* (negative measures from right edge) */
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JDIMENSION crop_yoffset; /* Y offset of selected region */
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JCROP_CODE crop_yoffset_set; /* (negative measures from bottom edge) */
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/* Internal workspace: caller should not touch these */
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int num_components; /* # of components in workspace */
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jvirt_barray_ptr * workspace_coef_arrays; /* workspace for transformations */
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JDIMENSION output_width; /* cropped destination dimensions */
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JDIMENSION output_height;
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JDIMENSION x_crop_offset; /* destination crop offsets measured in iMCUs */
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JDIMENSION y_crop_offset;
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int iMCU_sample_width; /* destination iMCU size */
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int iMCU_sample_height;
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} jpeg_transform_info;
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#if TRANSFORMS_SUPPORTED
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/* Parse a crop specification (written in X11 geometry style) */
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EXTERN(boolean) jtransform_parse_crop_spec
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JPP((jpeg_transform_info *info, const char *spec));
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/* Request any required workspace */
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EXTERN(boolean) jtransform_request_workspace
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JPP((j_decompress_ptr srcinfo, jpeg_transform_info *info));
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/* Adjust output image parameters */
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EXTERN(jvirt_barray_ptr *) jtransform_adjust_parameters
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JPP((j_decompress_ptr srcinfo, j_compress_ptr dstinfo,
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jvirt_barray_ptr *src_coef_arrays,
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jpeg_transform_info *info));
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/* Execute the actual transformation, if any */
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EXTERN(void) jtransform_execute_transform
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JPP((j_decompress_ptr srcinfo, j_compress_ptr dstinfo,
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jvirt_barray_ptr *src_coef_arrays,
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jpeg_transform_info *info));
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/* Determine whether lossless transformation is perfectly
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* possible for a specified image and transformation.
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*/
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EXTERN(boolean) jtransform_perfect_transform
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JPP((JDIMENSION image_width, JDIMENSION image_height,
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int MCU_width, int MCU_height,
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JXFORM_CODE transform));
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/* jtransform_execute_transform used to be called
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* jtransform_execute_transformation, but some compilers complain about
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* routine names that long. This macro is here to avoid breaking any
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* old source code that uses the original name...
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*/
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#define jtransform_execute_transformation jtransform_execute_transform
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#endif /* TRANSFORMS_SUPPORTED */
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/*
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* Support for copying optional markers from source to destination file.
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*/
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typedef enum {
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JCOPYOPT_NONE, /* copy no optional markers */
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JCOPYOPT_COMMENTS, /* copy only comment (COM) markers */
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JCOPYOPT_ALL /* copy all optional markers */
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} JCOPY_OPTION;
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#define JCOPYOPT_DEFAULT JCOPYOPT_COMMENTS /* recommended default */
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/* Setup decompression object to save desired markers in memory */
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EXTERN(void) jcopy_markers_setup
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JPP((j_decompress_ptr srcinfo, JCOPY_OPTION option));
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/* Copy markers saved in the given source object to the destination object */
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EXTERN(void) jcopy_markers_execute
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JPP((j_decompress_ptr srcinfo, j_compress_ptr dstinfo,
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JCOPY_OPTION option));
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