/*

* transupp.h

*

* 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 current 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.

*

* A complementary lossless-wipe option is provided to discard (gray out) data

* inside a given image region while losslessly preserving what is outside.

* Another option is lossless-drop, which replaces data at a given image

* position by another image. Both source images must have the same

* subsampling values. It is best if they also have the same quantization,

* otherwise quantization adaption occurs. The trim option can be used with

* the drop option to requantize the drop file to the source file.

*

* 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_WIPE, /* wipe */

JXFORM_DROP /* drop */

} JXFORM_CODE;

/*

* Codes for crop parameters, which can individually be unspecified,

* positive or negative for xoffset or yoffset,

*/

typedef enum {

JCROP_UNSET,

JCROP_POS,

JCROP_NEG,

JCROP_FORCE,

JCROP_REFLECT

} 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 */

/* 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 */

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) */

/* Drop parameters: set by caller for drop request */

j_decompress_ptr drop_ptr;

jvirt_barray_ptr * drop_coef_arrays;

/* 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;

JDIMENSION drop_width; /* drop/wipe dimensions measured in iMCUs */

JDIMENSION drop_height;

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));