chromium/third_party/libjpeg_turbo/rdcolmap.c

/*
 * rdcolmap.c
 *
 * Copyright (C) 1994-1996, Thomas G. Lane.
 * This file is part of the Independent JPEG Group's software.
 * For conditions of distribution and use, see the accompanying README.ijg
 * file.
 *
 * This file implements djpeg's "-map file" switch.  It reads a source image
 * and constructs a colormap to be supplied to the JPEG decompressor.
 *
 * Currently, these file formats are supported for the map file:
 *   GIF: the contents of the GIF's global colormap are used.
 *   PPM (either text or raw flavor): the entire file is read and
 *      each unique pixel value is entered in the map.
 * Note that reading a large PPM file will be horrendously slow.
 * Typically, a PPM-format map file should contain just one pixel
 * of each desired color.  Such a file can be extracted from an
 * ordinary image PPM file with ppmtomap(1).
 *
 * Rescaling a PPM that has a maxval unequal to MAXJSAMPLE is not
 * currently implemented.
 */

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

#ifdef QUANT_2PASS_SUPPORTED    /* otherwise can't quantize to supplied map */

/* Portions of this code are based on the PBMPLUS library, which is:
**
** Copyright (C) 1988 by Jef Poskanzer.
**
** Permission to use, copy, modify, and distribute this software and its
** documentation for any purpose and without fee is hereby granted, provided
** that the above copyright notice appear in all copies and that both that
** copyright notice and this permission notice appear in supporting
** documentation.  This software is provided "as is" without express or
** implied warranty.
*/


/*
 * Add a (potentially) new color to the color map.
 */

LOCAL(void)
add_map_entry(j_decompress_ptr cinfo, int R, int G, int B)
{ … }


/*
 * Extract color map from a GIF file.
 */

LOCAL(void)
read_gif_map(j_decompress_ptr cinfo, FILE *infile)
{ … }


/* Support routines for reading PPM */


LOCAL(int)
pbm_getc(FILE *infile)
/* Read next char, skipping over any comments */
/* A comment/newline sequence is returned as a newline */
{ … }


LOCAL(unsigned int)
read_pbm_integer(j_decompress_ptr cinfo, FILE *infile)
/* Read an unsigned decimal integer from the PPM file */
/* Swallows one trailing character after the integer */
/* Note that on a 16-bit-int machine, only values up to 64k can be read. */
/* This should not be a problem in practice. */
{ … }


/*
 * Extract color map from a PPM file.
 */

LOCAL(void)
read_ppm_map(j_decompress_ptr cinfo, FILE *infile)
{ … }


/*
 * Main entry point from djpeg.c.
 *  Input: opened input file (from file name argument on command line).
 *  Output: colormap and actual_number_of_colors fields are set in cinfo.
 */

GLOBAL(void)
read_color_map(j_decompress_ptr cinfo, FILE *infile)
{ … }

#endif /* QUANT_2PASS_SUPPORTED */