gimp/plug-ins/c_astretch/c_astretch.c

/* Contrast Autostretch 1.06 --- image filter plug-in for The Gimp image
 * manipulation program
 *
 * Copyright (C) 1996 Federico Mena Quintero
 *
 * You can contact me at quartic@polloux.fciencias.unam.mx
 * You can contact the original The Gimp authors at gimp@xcf.berkeley.edu
 *
 * 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., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

/* This simple plug-in does an automatic contrast stretch.  For each
   channel in the image, it finds the minimum and maximum values... it
   uses those values to stretch the individual histograms to the full
   contrast range.  For some images it may do just what you want; for
   others it may be total crap :) */


#include <stdlib.h>
#include <stdio.h>
#include "libgimp/gimp.h"

/* Declare local functions.
 */
static void      query  (void);
static void      run    (char      *name,
			 int        nparams,
			 GParam    *param,
			 int       *nreturn_vals,
			 GParam   **return_vals);

static void      c_astretch (GDrawable * drawable);
static void      indexed_c_astretch (gint32 image_ID);


GPlugInInfo PLUG_IN_INFO =
{
  NULL,    /* init_proc */
  NULL,    /* quit_proc */
  query,   /* query_proc */
  run,     /* run_proc */
};


MAIN ()

static void
query ()
{
  static GParamDef args[] =
  {
    { PARAM_INT32, "run_mode", "Interactive, non-interactive" },
    { PARAM_IMAGE, "image", "Input image" },
    { PARAM_DRAWABLE, "drawable", "Input drawable" },
  };
  static GParamDef *return_vals = NULL;
  static int nargs = sizeof (args) / sizeof (args[0]);
  static int nreturn_vals = 0;

  gimp_install_procedure ("plug_in_c_astretch",
			  "Automatically stretch the contrast of the specified drawable to cover all possible ranges.",
			  "This simple plug-in does an automatic contrast stretch.  For each channel in the image, it finds the minimum and maximum values... it uses those values to stretch the individual histograms to the full contrast range.  For some images it may do just what you want; for others it may be total crap :)",
			  "Federico Mena Quintero",
			  "Federico Mena Quintero",
			  "1996",
			  "<Image>/Filters/Image/Contrast Auto-Stretch",
			  "RGB*, GRAY*, INDEXED*",
			  PROC_PLUG_IN,
			  nargs, nreturn_vals,
			  args, return_vals);
}

static void
run (char    *name,
     int      nparams,
     GParam  *param,
     int     *nreturn_vals,
     GParam **return_vals)
{
  static GParam values[1];
  GDrawable *drawable;
  GRunModeType run_mode;
  GStatusType status = STATUS_SUCCESS;

  gint32 image_ID;

  run_mode = param[0].data.d_int32;

  /*  Get the specified drawable  */
  drawable = gimp_drawable_get (param[2].data.d_drawable);
  image_ID = param[1].data.d_image;

  /*  Make sure that the drawable is gray or RGB color  */
  if (gimp_drawable_color (drawable->id) || gimp_drawable_gray (drawable->id))
    {
      gimp_progress_init ("Auto-Stretching Contrast...");
      gimp_tile_cache_ntiles (2 * (drawable->width / gimp_tile_width () + 1));
      c_astretch (drawable);

      if (run_mode != RUN_NONINTERACTIVE)
	gimp_displays_flush ();
    }
  else if (gimp_drawable_indexed (drawable->id))
    {
      indexed_c_astretch (image_ID);

      /* GIMP doesn't implicitly update an image whose cmap has
	 changed - it probably should. */

      gimp_drawable_update (drawable->id, 0, 0,
			    gimp_drawable_width(drawable->id),
			    gimp_drawable_height(drawable->id));
      gimp_displays_flush ();
    }
  else
    {
      /* gimp_message ("c_astretch: cannot operate on indexed color images"); */
      status = STATUS_EXECUTION_ERROR;
    }

  *nreturn_vals = 1;
  *return_vals = values;

  values[0].type = PARAM_STATUS;
  values[0].data.d_status = status;

  gimp_drawable_detach (drawable);
}


static void
indexed_c_astretch(gint32 image_ID)  /* a.d.m. */
{
  guchar *cmap;
  gint ncols,i;
  gint rhi=0,ghi=0,bhi=0,rlo=255,glo=255,blo=255;

  cmap = gimp_image_get_cmap (image_ID, &ncols);

  if (cmap==NULL)
    {
      printf("c_astretch: cmap was NULL!  Quitting...\n");
      gimp_quit();
    }

  for (i=0;i<ncols;i++)
    {
      if (cmap[i*3 +0] > rhi) rhi=cmap[i*3 +0];
      if (cmap[i*3 +1] > ghi) ghi=cmap[i*3 +1];
      if (cmap[i*3 +2] > bhi) bhi=cmap[i*3 +2];
      if (cmap[i*3 +0] < rlo) rlo=cmap[i*3 +0];
      if (cmap[i*3 +1] < glo) glo=cmap[i*3 +1];
      if (cmap[i*3 +2] < blo) blo=cmap[i*3 +2];
    }

  for (i=0;i<ncols;i++)
    {
      if (rhi!=rlo)
	cmap[i*3 +0] = (255 * (cmap[i*3 +0] - rlo)) / (rhi-rlo);
      if (ghi!=glo)
	cmap[i*3 +1] = (255 * (cmap[i*3 +1] - glo)) / (ghi-glo);
      if (rhi!=rlo)
	cmap[i*3 +2] = (255 * (cmap[i*3 +2] - blo)) / (bhi-blo);
    }

  gimp_image_set_cmap (image_ID, cmap, ncols);
}


static void
c_astretch (GDrawable *drawable)
{
  GPixelRgn src_rgn, dest_rgn;
  guchar *src, *s;
  guchar *dest, *d;
  guchar  min[3], max[3];
  guchar  range;
  guchar  lut[256][3];
  gint    progress, max_progress;
  gint    has_alpha, alpha;
  gint    x1, y1, x2, y2;
  gint    x, y, b;
  gpointer pr;

  /* Get selection area */
  gimp_drawable_mask_bounds (drawable->id, &x1, &y1, &x2, &y2);
  has_alpha = gimp_drawable_has_alpha (drawable->id);
  alpha = (has_alpha) ? drawable->bpp - 1 : drawable->bpp;

  /* Initialize progress */
  progress = 0;
  max_progress = (x2 - x1) * (y2 - y1) * 2;

  /* Get minimum and maximum values for each channel */
  min[0] = min[1] = min[2] = 255;
  max[0] = max[1] = max[2] = 0;

  gimp_pixel_rgn_init (&src_rgn, drawable, x1, y1, (x2 - x1), (y2 - y1), FALSE, FALSE);

  for (pr = gimp_pixel_rgns_register (1, &src_rgn); pr != NULL; pr = gimp_pixel_rgns_process (pr))
    {
      src = src_rgn.data;

      for (y = 0; y < src_rgn.h; y++)
	{
	  s = src;
	  for (x = 0; x < src_rgn.w; x++)
	    {
	      for (b = 0; b < alpha; b++)
		{
		  if (!has_alpha || (has_alpha && s[alpha]))
		    {
		      if (s[b] < min[b])
			min[b] = s[b];
		      if (s[b] > max[b])
			max[b] = s[b];
		    }
		}

	      s += src_rgn.bpp;
	    }

	  src += src_rgn.rowstride;
	}

      /* Update progress */
      progress += src_rgn.w * src_rgn.h;

      gimp_progress_update ((double) progress / (double) max_progress);
    }

  /* Calculate LUTs with stretched contrast */
  for (b = 0; b < alpha; b++)
    {
      range = max[b] - min[b];

      if (range != 0)
	for (x = min[b]; x <= max[b]; x++)
	  lut[x][b] = 255 * (x - min[b]) / range;
      else
	lut[min[b]][b] = min[b];
    }

  /* Now substitute pixel vales */
  gimp_pixel_rgn_init (&src_rgn, drawable, x1, y1, (x2 - x1), (y2 - y1), FALSE, FALSE);
  gimp_pixel_rgn_init (&dest_rgn, drawable, x1, y1, (x2 - x1), (y2 - y1), TRUE, TRUE);

  for (pr = gimp_pixel_rgns_register (2, &src_rgn, &dest_rgn); pr != NULL; pr = gimp_pixel_rgns_process (pr))
    {
      src = src_rgn.data;
      dest = dest_rgn.data;

      for (y = 0; y < src_rgn.h; y++)
	{
	  s = src;
	  d = dest;

	  for (x = 0; x < src_rgn.w; x++)
	    {
	      for (b = 0; b < alpha; b++)
		d[b] = lut[s[b]][b];

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

	      s += src_rgn.bpp;
	      d += dest_rgn.bpp;
	    }

	  src += src_rgn.rowstride;
	  dest += dest_rgn.rowstride;

	}

      /* Update progress */
      progress += src_rgn.w * src_rgn.h;

      gimp_progress_update ((double) progress / (double) max_progress);
    }

  /*  update the region  */
  gimp_drawable_flush (drawable);
  gimp_drawable_merge_shadow (drawable->id, TRUE);
  gimp_drawable_update (drawable->id, x1, y1, (x2 - x1), (y2 - y1));
}