/*

 * 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 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)

{

  JSAMPROW colormap0 = cinfo->colormap[0];

  JSAMPROW colormap1 = cinfo->colormap[1];

  JSAMPROW colormap2 = cinfo->colormap[2];

  int ncolors = cinfo->actual_number_of_colors;

  int index;



  /* Check for duplicate color. */

  for (index = 0; index < ncolors; index++) {

    if (GETJSAMPLE(colormap0[index]) == R &&

	GETJSAMPLE(colormap1[index]) == G &&

	GETJSAMPLE(colormap2[index]) == B)

      return;			/* color is already in map */

  }



  /* Check for map overflow. */

  if (ncolors >= (MAXJSAMPLE+1))

    ERREXIT1(cinfo, JERR_QUANT_MANY_COLORS, (MAXJSAMPLE+1));



  /* OK, add color to map. */

  colormap0[ncolors] = (JSAMPLE) R;

  colormap1[ncolors] = (JSAMPLE) G;

  colormap2[ncolors] = (JSAMPLE) B;

  cinfo->actual_number_of_colors++;

}





/*

 * Extract color map from a GIF file.

 */



LOCAL(void)

read_gif_map (j_decompress_ptr cinfo, FILE * infile)

{

  int header[13];

  int i, colormaplen;

  int R, G, B;



  /* Initial 'G' has already been read by read_color_map */

  /* Read the rest of the GIF header and logical screen descriptor */

  for (i = 1; i < 13; i++) {

    if ((header[i] = getc(infile)) == EOF)

      ERREXIT(cinfo, JERR_BAD_CMAP_FILE);

  }



  /* Verify GIF Header */

  if (header[1] != 'I' || header[2] != 'F')

    ERREXIT(cinfo, JERR_BAD_CMAP_FILE);



  /* There must be a global color map. */

  if ((header[10] & 0x80) == 0)

    ERREXIT(cinfo, JERR_BAD_CMAP_FILE);



  /* OK, fetch it. */

  colormaplen = 2 << (header[10] & 0x07);



  for (i = 0; i < colormaplen; i++) {

    R = getc(infile);

    G = getc(infile);

    B = getc(infile);

    if (R == EOF || G == EOF || B == EOF)

      ERREXIT(cinfo, JERR_BAD_CMAP_FILE);

    add_map_entry(cinfo,

		  R << (BITS_IN_JSAMPLE-8),

		  G << (BITS_IN_JSAMPLE-8),

		  B << (BITS_IN_JSAMPLE-8));

  }

}





/* 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 */

{

  register int ch;

  

  ch = getc(infile);

  if (ch == '#') {

    do {

      ch = getc(infile);

    } while (ch != '\n' && ch != EOF);

  }

  return ch;

}





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. */

{

  register int ch;

  register unsigned int val;

  

  /* Skip any leading whitespace */

  do {

    ch = pbm_getc(infile);

    if (ch == EOF)

      ERREXIT(cinfo, JERR_BAD_CMAP_FILE);

  } while (ch == ' ' || ch == '\t' || ch == '\n' || ch == '\r');

  

  if (ch < '0' || ch > '9')

    ERREXIT(cinfo, JERR_BAD_CMAP_FILE);

  

  val = ch - '0';

  while ((ch = pbm_getc(infile)) >= '0' && ch <= '9') {

    val *= 10;

    val += ch - '0';

  }

  return val;

}





/*

 * Extract color map from a PPM file.

 */



LOCAL(void)

read_ppm_map (j_decompress_ptr cinfo, FILE * infile)

{

  int c;

  unsigned int w, h, maxval, row, col;

  int R, G, B;



  /* Initial 'P' has already been read by read_color_map */

  c = getc(infile);		/* save format discriminator for a sec */



  /* while we fetch the remaining header info */

  w = read_pbm_integer(cinfo, infile);

  h = read_pbm_integer(cinfo, infile);

  maxval = read_pbm_integer(cinfo, infile);



  if (w <= 0 || h <= 0 || maxval <= 0) /* error check */

    ERREXIT(cinfo, JERR_BAD_CMAP_FILE);



  /* For now, we don't support rescaling from an unusual maxval. */

  if (maxval != (unsigned int) MAXJSAMPLE)

    ERREXIT(cinfo, JERR_BAD_CMAP_FILE);



  switch (c) {

  case '3':			/* it's a text-format PPM file */

    for (row = 0; row < h; row++) {

      for (col = 0; col < w; col++) {

	R = read_pbm_integer(cinfo, infile);

	G = read_pbm_integer(cinfo, infile);

	B = read_pbm_integer(cinfo, infile);

	add_map_entry(cinfo, R, G, B);

      }

    }

    break;



  case '6':			/* it's a raw-format PPM file */

    for (row = 0; row < h; row++) {

      for (col = 0; col < w; col++) {

	R = getc(infile);

	G = getc(infile);

	B = getc(infile);

	if (R == EOF || G == EOF || B == EOF)

	  ERREXIT(cinfo, JERR_BAD_CMAP_FILE);

	add_map_entry(cinfo, R, G, B);

      }

    }

    break;



  default:

    ERREXIT(cinfo, JERR_BAD_CMAP_FILE);

    break;

  }

}





/*

 * 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)

{

  /* Allocate space for a color map of maximum supported size. */

  cinfo->colormap = (*cinfo->mem->alloc_sarray)

    ((j_common_ptr) cinfo, JPOOL_IMAGE,

     (JDIMENSION) (MAXJSAMPLE+1), (JDIMENSION) 3);

  cinfo->actual_number_of_colors = 0; /* initialize map to empty */



  /* Read first byte to determine file format */

  switch (getc(infile)) {

  case 'G':

    read_gif_map(cinfo, infile);

    break;

  case 'P':

    read_ppm_map(cinfo, infile);

    break;

  default:

    ERREXIT(cinfo, JERR_BAD_CMAP_FILE);

    break;

  }

}



#endif /* QUANT_2PASS_SUPPORTED */

