gimp/app/base/threshold.c

/* The GIMP -- an image manipulation program
 * Copyright (C) 1995 Spencer Kimball and Peter Mattis
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 */

#include "config.h"

#include <glib-object.h>

#include "base-types.h"

#include "pixel-region.h"
#include "threshold.h"


void
threshold_2 (gpointer     data,
	     PixelRegion *srcPR,
	     PixelRegion *destPR)
{
  threshold (srcPR, destPR, data);
}

void
threshold (PixelRegion *srcPR,
	   PixelRegion *destPR,
	   gpointer     data)
{
  Threshold *tr;
  guchar    *src, *s;
  guchar    *dest, *d;
  gint       has_alpha, alpha;
  gint       w, h, b;
  gint       value;

  tr = (Threshold *) data;

  h         = srcPR->h;
  src       = srcPR->data;
  dest      = destPR->data;
  has_alpha = (srcPR->bytes == 2 || srcPR->bytes == 4);
  alpha     = has_alpha ? srcPR->bytes - 1 : srcPR->bytes;

  while (h--)
    {
      w = srcPR->w;
      s = src;
      d = dest;

      while (w--)
	{
	  if (tr->color)
	    {
	      value = MAX (s[RED_PIX], s[GREEN_PIX]);
	      value = MAX (value, s[BLUE_PIX]);

	      value = (value >= tr->low_threshold && value <= tr->high_threshold ) ? 255 : 0;
	    }
	  else
	    value = (s[GRAY_PIX] >= tr->low_threshold && s[GRAY_PIX] <= tr->high_threshold) ? 255 : 0;

	  for (b = 0; b < alpha; b++)
	    d[b] = value;

	  if (has_alpha)
	    d[alpha] = s[alpha];

	  s += srcPR->bytes;
	  d += destPR->bytes;
	}

      src  += srcPR->rowstride;
      dest += destPR->rowstride;
    }
}