view release on metacpan or  search on metacpan

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

/*
 * rdrle.c
 *
 * Copyright (C) 1991-1996, 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 routines to read input images in Utah RLE format.
 * The Utah Raster Toolkit library is required (version 3.1 or later).
 *
 * These routines may need modification for non-Unix environments or
 * specialized applications.  As they stand, they assume input from
 * an ordinary stdio stream.  They further assume that reading begins
 * at the start of the file; start_input may need work if the
 * user interface has already read some data (e.g., to determine that
 * the file is indeed RLE format).
 *
 * Based on code contributed by Mike Lijewski,
 * with updates from Robert Hutchinson.
 */

#include "cdjpeg.h"		/* Common decls for cjpeg/djpeg applications */

#ifdef RLE_SUPPORTED

/* rle.h is provided by the Utah Raster Toolkit. */

#include <rle.h>

/*
 * We assume that JSAMPLE has the same representation as rle_pixel,
 * to wit, "unsigned char".  Hence we can't cope with 12- or 16-bit samples.
 */

#if BITS_IN_JSAMPLE != 8
  Sorry, this code only copes with 8-bit JSAMPLEs. /* deliberate syntax err */
#endif

/*
 * We support the following types of RLE files:
 *   
 *   GRAYSCALE   - 8 bits, no colormap
 *   MAPPEDGRAY  - 8 bits, 1 channel colomap
 *   PSEUDOCOLOR - 8 bits, 3 channel colormap
 *   TRUECOLOR   - 24 bits, 3 channel colormap
 *   DIRECTCOLOR - 24 bits, no colormap
 *
 * For now, we ignore any alpha channel in the image.
 */

typedef enum
  { GRAYSCALE, MAPPEDGRAY, PSEUDOCOLOR, TRUECOLOR, DIRECTCOLOR } rle_kind;


/*
 * Since RLE stores scanlines bottom-to-top, we have to invert the image
 * to conform to JPEG's top-to-bottom order.  To do this, we read the
 * incoming image into a virtual array on the first get_pixel_rows call,
 * then fetch the required row from the virtual array on subsequent calls.
 */

typedef struct _rle_source_struct * rle_source_ptr;

typedef struct _rle_source_struct {
  struct cjpeg_source_struct pub; /* public fields */

  rle_kind visual;              /* actual type of input file */
  jvirt_sarray_ptr image;       /* virtual array to hold the image */
  JDIMENSION row;		/* current row # in the virtual array */
  rle_hdr header;               /* Input file information */
  rle_pixel** rle_row;          /* holds a row returned by rle_getrow() */