view release on metacpan or  search on metacpan

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

  j_compress_ptr cinfo;		/* back link saves passing separate parm */

  JSAMPARRAY colormap;		/* BMP colormap (converted to my format) */

  jvirt_sarray_ptr whole_image;	/* Needed to reverse row order */
  JDIMENSION source_row;	/* Current source row number */
  JDIMENSION row_width;		/* Physical width of scanlines in file */

  int bits_per_pixel;		/* remembers 8- or 24-bit format */
} bmp_source_struct;


LOCAL(int)
read_byte (bmp_source_ptr sinfo)
/* Read next byte from BMP file */
{
  register FILE *infile = sinfo->pub.input_file;
  register int c;

  if ((c = getc(infile)) == EOF)
    ERREXIT(sinfo->cinfo, JERR_INPUT_EOF);
  return c;
}


LOCAL(void)
read_colormap (bmp_source_ptr sinfo, int cmaplen, int mapentrysize)
/* Read the colormap from a BMP file */
{
  int i;

  switch (mapentrysize) {
  case 3:
    /* BGR format (occurs in OS/2 files) */
    for (i = 0; i < cmaplen; i++) {
      sinfo->colormap[2][i] = (JSAMPLE) read_byte(sinfo);
      sinfo->colormap[1][i] = (JSAMPLE) read_byte(sinfo);
      sinfo->colormap[0][i] = (JSAMPLE) read_byte(sinfo);
    }
    break;
  case 4:
    /* BGR0 format (occurs in MS Windows files) */
    for (i = 0; i < cmaplen; i++) {
      sinfo->colormap[2][i] = (JSAMPLE) read_byte(sinfo);
      sinfo->colormap[1][i] = (JSAMPLE) read_byte(sinfo);
      sinfo->colormap[0][i] = (JSAMPLE) read_byte(sinfo);
      (void) read_byte(sinfo);
    }
    break;
  default:
    ERREXIT(sinfo->cinfo, JERR_BMP_BADCMAP);
    break;
  }
}


/*
 * Read one row of pixels.
 * The image has been read into the whole_image array, but is otherwise
 * unprocessed.  We must read it out in top-to-bottom row order, and if
 * it is an 8-bit image, we must expand colormapped pixels to 24bit format.
 */

METHODDEF(JDIMENSION)
get_8bit_row (j_compress_ptr cinfo, cjpeg_source_ptr sinfo)
/* This version is for reading 8-bit colormap indexes */
{
  bmp_source_ptr source = (bmp_source_ptr) sinfo;
  register JSAMPARRAY colormap = source->colormap;
  JSAMPARRAY image_ptr;
  register int t;
  register JSAMPROW inptr, outptr;
  register JDIMENSION col;

  /* Fetch next row from virtual array */
  source->source_row--;
  image_ptr = (*cinfo->mem->access_virt_sarray)
    ((j_common_ptr) cinfo, source->whole_image,
     source->source_row, (JDIMENSION) 1, FALSE);

  /* Expand the colormap indexes to real data */
  inptr = image_ptr[0];
  outptr = source->pub.buffer[0];
  for (col = cinfo->image_width; col > 0; col--) {
    t = GETJSAMPLE(*inptr++);
    *outptr++ = colormap[0][t];	/* can omit GETJSAMPLE() safely */
    *outptr++ = colormap[1][t];
    *outptr++ = colormap[2][t];
  }

  return 1;
}


METHODDEF(JDIMENSION)
get_24bit_row (j_compress_ptr cinfo, cjpeg_source_ptr sinfo)
/* This version is for reading 24-bit pixels */
{
  bmp_source_ptr source = (bmp_source_ptr) sinfo;
  JSAMPARRAY image_ptr;
  register JSAMPROW inptr, outptr;
  register JDIMENSION col;

  /* Fetch next row from virtual array */
  source->source_row--;
  image_ptr = (*cinfo->mem->access_virt_sarray)
    ((j_common_ptr) cinfo, source->whole_image,
     source->source_row, (JDIMENSION) 1, FALSE);

  /* Transfer data.  Note source values are in BGR order
   * (even though Microsoft's own documents say the opposite).
   */
  inptr = image_ptr[0];
  outptr = source->pub.buffer[0];
  for (col = cinfo->image_width; col > 0; col--) {
    outptr[2] = *inptr++;	/* can omit GETJSAMPLE() safely */
    outptr[1] = *inptr++;
    outptr[0] = *inptr++;
    outptr += 3;
  }