gimp/plug-ins/common/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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, 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 not work that well */

#include "config.h"

#include <stdlib.h>
#include <stdio.h>

#include <libgimp/gimp.h>

#include "libgimp/stdplugins-intl.h"


/* Declare local functions.
 */
static void   query              (void);
static void   run                (const gchar      *name,
                                  gint              nparams,
                                  const GimpParam  *param,
                                  gint             *nreturn_vals,
                                  GimpParam       **return_vals);

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


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

static GimpRunMode run_mode;

MAIN ()

static void
query (void)
{
  static GimpParamDef args[] =
  {
    { GIMP_PDB_INT32, "run_mode", "Interactive, non-interactive" },
    { GIMP_PDB_IMAGE, "image", "Input image" },
    { GIMP_PDB_DRAWABLE, "drawable", "Input drawable" }
  };

  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 not work "
			  "that well.",
			  "Federico Mena Quintero",
			  "Federico Mena Quintero",
			  "1996",
			  N_("<Image>/Layer/Colors/Auto/_Stretch Contrast"),
			  "RGB*, GRAY*, INDEXED*",
			  GIMP_PLUGIN,
			  G_N_ELEMENTS (args), 0,
			  args, NULL);
}

static void
run (const gchar      *name,
     gint              nparams,
     const GimpParam  *param,
     gint             *nreturn_vals,
     GimpParam       **return_vals)
{
  static GimpParam   values[1];
  GimpDrawable      *drawable;
  GimpPDBStatusType  status = GIMP_PDB_SUCCESS;

  gint32 image_ID;

  INIT_I18N();

  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_is_rgb (drawable->drawable_id) ||
      gimp_drawable_is_gray (drawable->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 != GIMP_RUN_NONINTERACTIVE)
	gimp_displays_flush ();
    }
  else if (gimp_drawable_is_indexed (drawable->drawable_id))
    {
      indexed_c_astretch (image_ID);

      if (run_mode != GIMP_RUN_NONINTERACTIVE)
	gimp_displays_flush ();
    }
  else
    {
      /* gimp_message ("c_astretch: cannot operate on indexed color images"); */
      status = GIMP_PDB_EXECUTION_ERROR;
    }

  *nreturn_vals = 1;
  *return_vals = values;

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

  gimp_drawable_detach (drawable);
}

static void
indexed_c_astretch (gint32 image_ID)
{
  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);
}

typedef struct {
  gint		alpha;
  guchar  	lut[256][3];
  guchar  	min[3];
  guchar	max[3];
  gboolean 	has_alpha;
} AutoStretchParam_t;

static void
find_min_max (const guchar *src,
              gint         bpp,
              gpointer     data)
{
  AutoStretchParam_t *param = (AutoStretchParam_t*) data;
  gint b;

  for (b = 0; b < param->alpha; b++)
    {
      if (!param->has_alpha || src[param->alpha])
	{
	  if (src[b] < param->min[b])
	    param->min[b] = src[b];
	  if (src[b] > param->max[b])
	    param->max[b] = src[b];
	}
    }
}

static void
c_astretch_func (const guchar *src,
                 guchar       *dest,
                 gint          bpp,
                 gpointer      data)
{
  AutoStretchParam_t *param = (AutoStretchParam_t*) data;
  gint b;

  for (b = 0; b < param->alpha; b++)
    dest[b] = param->lut[src[b]][b];

  if (param->has_alpha)
    dest[param->alpha] = src[param->alpha];
}

static void
c_astretch (GimpDrawable *drawable)
{
  AutoStretchParam_t param;
  gint b;

  param.has_alpha = gimp_drawable_has_alpha (drawable->drawable_id);
  param.alpha = (param.has_alpha) ? drawable->bpp - 1 : drawable->bpp;

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

  gimp_rgn_iterate1 (drawable, run_mode, find_min_max, &param);

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

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

  gimp_rgn_iterate2 (drawable, run_mode, c_astretch_func, &param);
}