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src/Source/LibJPEG/transupp.c  view on Meta::CPAN

/*
 * transupp.c
 *
 * Copyright (C) 1997-2013, 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 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.
 */

/* Although this file really shouldn't have access to the library internals,
 * it's helpful to let it call jround_up() and jcopy_block_row().
 */
#define JPEG_INTERNALS

#include "jinclude.h"
#include "jpeglib.h"
#include "transupp.h"		/* My own external interface */
#include <ctype.h>		/* to declare isdigit() */


#if TRANSFORMS_SUPPORTED

/*
 * Lossless image transformation routines.  These routines work on DCT
 * coefficient arrays and thus do not require any lossy decompression
 * or recompression of the image.
 * Thanks to Guido Vollbeding for the initial design and code of this feature,
 * and to Ben Jackson for introducing the cropping feature.
 *
 * Horizontal flipping is done in-place, using a single top-to-bottom
 * pass through the virtual source array.  It will thus be much the
 * fastest option for images larger than main memory.
 *
 * The other routines require a set of destination virtual arrays, so they
 * need twice as much memory as jpegtran normally does.  The destination
 * arrays are always written in normal scan order (top to bottom) because
 * the virtual array manager expects this.  The source arrays will be scanned
 * in the corresponding order, which means multiple passes through the source
 * arrays for most of the transforms.  That could result in much thrashing
 * if the image is larger than main memory.
 *
 * If cropping or trimming is involved, the destination arrays may be smaller
 * than the source arrays.  Note it is not possible to do horizontal flip
 * in-place when a nonzero Y crop offset is specified, since we'd have to move
 * data from one block row to another but the virtual array manager doesn't
 * guarantee we can touch more than one row at a time.  So in that case,
 * we have to use a separate destination array.
 *
 * Some notes about the operating environment of the individual transform
 * routines:
 * 1. Both the source and destination virtual arrays are allocated from the
 *    source JPEG object, and therefore should be manipulated by calling the
 *    source's memory manager.
 * 2. The destination's component count should be used.  It may be smaller
 *    than the source's when forcing to grayscale.
 * 3. Likewise the destination's sampling factors should be used.  When
 *    forcing to grayscale the destination's sampling factors will be all 1,
 *    and we may as well take that as the effective iMCU size.
 * 4. When "trim" is in effect, the destination's dimensions will be the
 *    trimmed values but the source's will be untrimmed.
 * 5. When "crop" is in effect, the destination's dimensions will be the
 *    cropped values but the source's will be uncropped.  Each transform
 *    routine is responsible for picking up source data starting at the
 *    correct X and Y offset for the crop region.  (The X and Y offsets
 *    passed to the transform routines are measured in iMCU blocks of the
 *    destination.)
 * 6. All the routines assume that the source and destination buffers are
 *    padded out to a full iMCU boundary.  This is true, although for the
 *    source buffer it is an undocumented property of jdcoefct.c.
 */


LOCAL(void)
do_crop (j_decompress_ptr srcinfo, j_compress_ptr dstinfo,
	 JDIMENSION x_crop_offset, JDIMENSION y_crop_offset,
	 jvirt_barray_ptr *src_coef_arrays,
	 jvirt_barray_ptr *dst_coef_arrays)
/* Crop.  This is only used when no rotate/flip is requested with the crop. */
{
  JDIMENSION dst_blk_y, x_crop_blocks, y_crop_blocks;
  int ci, offset_y;
  JBLOCKARRAY src_buffer, dst_buffer;
  jpeg_component_info *compptr;

src/Source/LibJPEG/transupp.c  view on Meta::CPAN

			      j_compress_ptr dstinfo,
			      jvirt_barray_ptr *src_coef_arrays,
			      jpeg_transform_info *info)
{
  jvirt_barray_ptr *dst_coef_arrays = info->workspace_coef_arrays;

  /* Note: conditions tested here should match those in switch statement
   * in jtransform_request_workspace()
   */
  switch (info->transform) {
  case JXFORM_NONE:
    if (info->output_width > srcinfo->output_width ||
	info->output_height > srcinfo->output_height)
      do_crop_ext(srcinfo, dstinfo, info->x_crop_offset, info->y_crop_offset,
		  src_coef_arrays, dst_coef_arrays);
    else if (info->x_crop_offset != 0 || info->y_crop_offset != 0)
      do_crop(srcinfo, dstinfo, info->x_crop_offset, info->y_crop_offset,
	      src_coef_arrays, dst_coef_arrays);
    break;
  case JXFORM_FLIP_H:
    if (info->y_crop_offset != 0)
      do_flip_h(srcinfo, dstinfo, info->x_crop_offset, info->y_crop_offset,
		src_coef_arrays, dst_coef_arrays);
    else
      do_flip_h_no_crop(srcinfo, dstinfo, info->x_crop_offset,
			src_coef_arrays);
    break;
  case JXFORM_FLIP_V:
    do_flip_v(srcinfo, dstinfo, info->x_crop_offset, info->y_crop_offset,
	      src_coef_arrays, dst_coef_arrays);
    break;
  case JXFORM_TRANSPOSE:
    do_transpose(srcinfo, dstinfo, info->x_crop_offset, info->y_crop_offset,
		 src_coef_arrays, dst_coef_arrays);
    break;
  case JXFORM_TRANSVERSE:
    do_transverse(srcinfo, dstinfo, info->x_crop_offset, info->y_crop_offset,
		  src_coef_arrays, dst_coef_arrays);
    break;
  case JXFORM_ROT_90:
    do_rot_90(srcinfo, dstinfo, info->x_crop_offset, info->y_crop_offset,
	      src_coef_arrays, dst_coef_arrays);
    break;
  case JXFORM_ROT_180:
    do_rot_180(srcinfo, dstinfo, info->x_crop_offset, info->y_crop_offset,
	       src_coef_arrays, dst_coef_arrays);
    break;
  case JXFORM_ROT_270:
    do_rot_270(srcinfo, dstinfo, info->x_crop_offset, info->y_crop_offset,
	       src_coef_arrays, dst_coef_arrays);
    break;
  case JXFORM_WIPE:
    do_wipe(srcinfo, dstinfo, info->x_crop_offset, info->y_crop_offset,
	    src_coef_arrays, info->drop_width, info->drop_height);
    break;
  }
}

/* jtransform_perfect_transform
 *
 * Determine whether lossless transformation is perfectly
 * possible for a specified image and transformation.
 *
 * Inputs:
 *   image_width, image_height: source image dimensions.
 *   MCU_width, MCU_height: pixel dimensions of MCU.
 *   transform: transformation identifier.
 * Parameter sources from initialized jpeg_struct
 * (after reading source header):
 *   image_width = cinfo.image_width
 *   image_height = cinfo.image_height
 *   MCU_width = cinfo.max_h_samp_factor * cinfo.block_size
 *   MCU_height = cinfo.max_v_samp_factor * cinfo.block_size
 * Result:
 *   TRUE = perfect transformation possible
 *   FALSE = perfect transformation not possible
 *           (may use custom action then)
 */

GLOBAL(boolean)
jtransform_perfect_transform(JDIMENSION image_width, JDIMENSION image_height,
			     int MCU_width, int MCU_height,
			     JXFORM_CODE transform)
{
  boolean result = TRUE; /* initialize TRUE */

  switch (transform) {
  case JXFORM_FLIP_H:
  case JXFORM_ROT_270:
    if (image_width % (JDIMENSION) MCU_width)
      result = FALSE;
    break;
  case JXFORM_FLIP_V:
  case JXFORM_ROT_90:
    if (image_height % (JDIMENSION) MCU_height)
      result = FALSE;
    break;
  case JXFORM_TRANSVERSE:
  case JXFORM_ROT_180:
    if (image_width % (JDIMENSION) MCU_width)
      result = FALSE;
    if (image_height % (JDIMENSION) MCU_height)
      result = FALSE;
    break;
  default:
    break;
  }

  return result;
}

#endif /* TRANSFORMS_SUPPORTED */


/* Setup decompression object to save desired markers in memory.
 * This must be called before jpeg_read_header() to have the desired effect.
 */

GLOBAL(void)
jcopy_markers_setup (j_decompress_ptr srcinfo, JCOPY_OPTION option)
{