File indexing completed on 2024-05-19 04:21:26

 /*
  * 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));