gimp/plug-ins/common/decompose.c

/* The GIMP -- an image manipulation program
 * Copyright (C) 1995 Spencer Kimball and Peter Mattis
 *
 * Decompose plug-in (C) 1997 Peter Kirchgessner
 * e-mail: peter@kirchgessner.net, WWW: http://www.kirchgessner.net
 *
 * 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 filter decomposes RGB-images into several types of channels
 */

/* Event history:
 * V 1.00, PK, 29-Jul-97, Creation
 * V 1.01, PK, 19-Mar-99, Update for GIMP V1.1.3
 *                        Prepare for localization
 *                        Use g_message() in interactive mode
 */
static char ident[] = "@(#) GIMP Decompose plug-in v1.01 19-Mar-99";

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

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

#include <gtk/gtk.h>

#include <libgimp/gimp.h>
#include <libgimp/gimpui.h>

#include "libgimp/stdplugins-intl.h"


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

static gint32    decompose (gint32  image_id,
                            gint32  drawable_ID,
                            gchar   *extract_type,
                            gint32  *drawable_ID_dst);

static gint32 create_new_image (gchar       *filename,
				guint        width,
				guint        height,
				GimpImageBaseType   type,
				gint32      *layer_ID,
				GimpDrawable  **drawable,
				GimpPixelRgn   *pixel_rgn);

static void extract_rgb      (guchar *src, gint bpp, gint numpix, guchar **dst);
static void extract_red      (guchar *src, gint bpp, gint numpix, guchar **dst);
static void extract_green    (guchar *src, gint bpp, gint numpix, guchar **dst);
static void extract_blue     (guchar *src, gint bpp, gint numpix, guchar **dst);
static void extract_alpha    (guchar *src, gint bpp, gint numpix, guchar **dst);
static void extract_hsv      (guchar *src, gint bpp, gint numpix, guchar **dst);
static void extract_hue      (guchar *src, gint bpp, gint numpix, guchar **dst);
static void extract_sat      (guchar *src, gint bpp, gint numpix, guchar **dst);
static void extract_val      (guchar *src, gint bpp, gint numpix, guchar **dst);
static void extract_cmy      (guchar *src, gint bpp, gint numpix, guchar **dst);
static void extract_cyan     (guchar *src, gint bpp, gint numpix, guchar **dst);
static void extract_magenta  (guchar *src, gint bpp, gint numpix, guchar **dst);
static void extract_yellow   (guchar *src, gint bpp, gint numpix, guchar **dst);
static void extract_cmyk     (guchar *src, gint bpp, gint numpix, guchar **dst);
static void extract_cyank    (guchar *src, gint bpp, gint numpix, guchar **dst);
static void extract_magentak (guchar *src, gint bpp, gint numpix, guchar **dst);
static void extract_yellowk  (guchar *src, gint bpp, gint numpix, guchar **dst);

static gint decompose_dialog      (void);
static void decompose_ok_callback (GtkWidget *widget,
				   gpointer   data);

/* Maximum number of new images generated by an extraction */
#define MAX_EXTRACT_IMAGES 4

/* Description of an extraction */
typedef struct
{
  gchar *type;            /* What to extract */
  gint   dialog;          /* Dialog-Flag. Set it to 1 if you want to appear */
                          /* this extract function within the dialog */
  gint   num_images;      /* Number of images to create */
  gchar *channel_name[MAX_EXTRACT_IMAGES];   /* Names of channels to extract */
                          /* Function that performs the extraction */
  void (*extract_fun) (guchar *src, int bpp, gint numpix,
			guchar **dst);
} EXTRACT;

static EXTRACT extract[] =
{
  { N_("RGB"),        TRUE,  3, { N_("red"),
				  N_("green"),
				  N_("blue") }, extract_rgb },
  { N_("Red"),        FALSE, 1, { N_("red") }, extract_red },
  { N_("Green"),      FALSE, 1, { N_("green") }, extract_green },
  { N_("Blue"),       FALSE, 1, { N_("blue") }, extract_blue },
  { N_("HSV"),        TRUE,  3, { N_("hue"),
				  N_("saturation"),
				  N_("value") }, extract_hsv },
  { N_("Hue"),        FALSE, 1, { N_("hue") }, extract_hue },
  { N_("Saturation"), FALSE, 1, { N_("saturation") }, extract_sat },
  { N_("Value"),      FALSE, 1, { N_("value") }, extract_val },
  { N_("CMY"),        TRUE,  3, { N_("cyan"),
				  N_("magenta"),
				  N_("yellow") }, extract_cmy },
  { N_("Cyan"),       FALSE, 1, { N_("cyan") }, extract_cyan },
  { N_("Magenta"),    FALSE, 1, { N_("magenta") }, extract_magenta },
  { N_("Yellow"),     FALSE, 1, { N_("yellow") }, extract_yellow },
  { N_("CMYK"),       TRUE,  4, { N_("cyan_k"),
				  N_("magenta_k"),
				  N_("yellow_k"),
				  N_("black") }, extract_cmyk },
  { N_("Cyan_K"),     FALSE, 1, { N_("cyan_k") }, extract_cyank },
  { N_("Magenta_K"),  FALSE, 1, { N_("magenta_k") }, extract_magentak },
  { N_("Yellow_K"),   FALSE, 1, { N_("yellow_k") }, extract_yellowk },
  { N_("Alpha"),      TRUE,  1, { N_("alpha") }, extract_alpha }
};

/* Number of types of extractions */
#define NUM_EXTRACT_TYPES (sizeof (extract) / sizeof (extract[0]))

typedef struct
{
  gchar extract_type[32];
} DecoVals;

typedef struct
{
  gint extract_flag[NUM_EXTRACT_TYPES];
  gint run;
} DecoInterface;

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

static DecoVals decovals =
{
  "rgb"     /* Decompose type */
};

static DecoInterface decoint =
{
  { 0 },    /*  extract flags */
  FALSE     /*  run  */
};

static GimpRunModeType run_mode;


MAIN ()

static void
query (void)
{
  static GimpParamDef args[] =
  {
    { GIMP_PDB_INT32, "run_mode", "Interactive, non-interactive" },
    { GIMP_PDB_IMAGE, "image", "Input image (unused)" },
    { GIMP_PDB_DRAWABLE, "drawable", "Input drawable" },
    { GIMP_PDB_STRING, "decompose_type", "What to decompose: RGB, Red, Green, Blue, HSV, Hue, Saturation, Value, CMY, Cyan, Magenta, Yellow, CMYK, Cyan_K, Magenta_K, Yellow_K, Alpha" }
  };
  static GimpParamDef return_vals[] =
  {
    { GIMP_PDB_IMAGE, "new_image", "Output gray image" },
    { GIMP_PDB_IMAGE, "new_image", "Output gray image (N/A for single channel extract)" },
    { GIMP_PDB_IMAGE, "new_image", "Output gray image (N/A for single channel extract)" },
    { GIMP_PDB_IMAGE, "new_image", "Output gray image (N/A for single channel extract)" }
  };
  static gint nargs = sizeof (args) / sizeof (args[0]);
  static gint nreturn_vals = sizeof (return_vals) / sizeof (return_vals[0]);

  gimp_install_procedure ("plug_in_decompose",
			  "Decompose an image into different types of channels",
			  "This function creates new gray images with "
			  "different channel information in each of them",
			  "Peter Kirchgessner",
			  "Peter Kirchgessner (peter@kirchgessner.net)",
			  "1997",
			  N_("<Image>/Image/Mode/Decompose..."),
			  "RGB*",
			  GIMP_PLUGIN,
			  nargs, nreturn_vals,
			  args, return_vals);
}

static void
run (gchar   *name,
     gint     nparams,
     GimpParam  *param,
     gint    *nreturn_vals,
     GimpParam **return_vals)
{
  static GimpParam values[MAX_EXTRACT_IMAGES+1];
  GimpPDBStatusType status = GIMP_PDB_SUCCESS;
  GimpImageType drawable_type;
  gint32 num_images;
  gint32 image_ID_extract[MAX_EXTRACT_IMAGES];
  gint j;

  INIT_I18N_UI();

  run_mode = param[0].data.d_int32;

  *nreturn_vals = MAX_EXTRACT_IMAGES+1;
  *return_vals = values;

  values[0].type = GIMP_PDB_STATUS;
  values[0].data.d_status = status;
  for (j = 0; j < MAX_EXTRACT_IMAGES; j++)
    {
      values[j+1].type = GIMP_PDB_IMAGE;
      values[j+1].data.d_int32 = -1;
    }

  switch (run_mode)
    {
    case GIMP_RUN_INTERACTIVE:
      /*  Possibly retrieve data  */
      gimp_get_data ("plug_in_decompose", &decovals);

      /*  First acquire information with a dialog  */
      if (! decompose_dialog ())
	return;
      break;

    case GIMP_RUN_NONINTERACTIVE:
      /*  Make sure all the arguments are there!  */
      if (nparams != 4)
	{
	  status = GIMP_PDB_CALLING_ERROR;
	}
      else
	{
          strncpy (decovals.extract_type, param[3].data.d_string,
                   sizeof (decovals.extract_type));
          decovals.extract_type[sizeof (decovals.extract_type)-1] = '\0';
	}
      break;

    case GIMP_RUN_WITH_LAST_VALS:
      /*  Possibly retrieve data  */
      gimp_get_data ("plug_in_decompose", &decovals);
      break;

    default:
      break;
    }

  /*  Make sure that the drawable is RGB color  */
  drawable_type = gimp_drawable_type (param[2].data.d_drawable);
  if ((drawable_type != GIMP_RGB_IMAGE) && (drawable_type != GIMP_RGBA_IMAGE))
    {
      g_message ("decompose: Can only work on RGB*_IMAGE");
      status = GIMP_PDB_CALLING_ERROR;
    }
  if (status == GIMP_PDB_SUCCESS)
    {
      if (run_mode != GIMP_RUN_NONINTERACTIVE)
        gimp_progress_init (_("Decomposing..."));
      
      num_images = decompose (param[1].data.d_image, param[2].data.d_drawable,
                              decovals.extract_type, image_ID_extract);
      
      if (num_images <= 0)
	{
	  status = GIMP_PDB_EXECUTION_ERROR;
	}
      else
	{
	  for (j = 0; j < num_images; j++)
	    {
	      values[j+1].data.d_int32 = image_ID_extract[j];
	      gimp_image_undo_enable (image_ID_extract[j]);
	      gimp_image_clean_all (image_ID_extract[j]);
	      if (run_mode != GIMP_RUN_NONINTERACTIVE)
		gimp_display_new (image_ID_extract[j]);
	    }
	  
	  /*  Store data  */
	  if (run_mode == GIMP_RUN_INTERACTIVE)
	    gimp_set_data ("plug_in_decompose", &decovals, sizeof (DecoVals));
	}
    }
  
  values[0].data.d_status = status;
}


/* Decompose an image. It returns the number of new (gray) images.
   The image IDs for the new images are returned in image_ID_dst.
   On failure, -1 is returned.
*/
static gint32
decompose (gint32  image_ID,
           gint32  drawable_ID,
           char   *extract_type,
           gint32 *image_ID_dst)
{
  gint i, j, extract_idx, scan_lines;
  gint height, width, tile_height, num_images;
  guchar *src = (guchar *)ident;  /* Just to satisfy gcc/lint */
  gchar *filename;
  guchar *dst[MAX_EXTRACT_IMAGES];
  gint32 layer_ID_dst[MAX_EXTRACT_IMAGES];
  GimpDrawable *drawable_src, *drawable_dst[MAX_EXTRACT_IMAGES];
  GimpPixelRgn pixel_rgn_src, pixel_rgn_dst[MAX_EXTRACT_IMAGES];

  extract_idx = -1;   /* Search extract type */
  for (j = 0; j < NUM_EXTRACT_TYPES; j++)
    {
      if (g_strcasecmp (extract_type, extract[j].type) == 0)
	{
	  extract_idx = j;
	  break;
	}
    }
  if (extract_idx < 0) return (-1);
  
  /* Check structure of source image */
  drawable_src = gimp_drawable_get (drawable_ID);
  if (drawable_src->bpp < 3)
    {
      g_message ("decompose: not an RGB image");
      return (-1);
    }
  if ((extract[extract_idx].extract_fun == extract_alpha) &&
      (!gimp_drawable_has_alpha (drawable_ID)))
    {
      g_message ("decompose: No alpha channel available");
      return (-1);
    }
  
  width = drawable_src->width;
  height = drawable_src->height;

  tile_height = gimp_tile_height ();
  gimp_pixel_rgn_init (&pixel_rgn_src, drawable_src, 0, 0, width, height,
                       FALSE, FALSE);

  /* allocate a buffer for retrieving information from the src pixel region  */
  src = g_new (guchar, tile_height * width * drawable_src->bpp);

  /* Create all new gray images */
  num_images = extract[extract_idx].num_images;
  if (num_images > MAX_EXTRACT_IMAGES) 
    num_images = MAX_EXTRACT_IMAGES;
  
  for (j = 0; j < num_images; j++)
    {
      /* Build a filename like <imagename>-<channel>.<extension> */
      char *fname = g_strdup (gimp_image_get_filename (image_ID));
      char *extension = fname + strlen (fname) - 1;

      while (extension >= fname)
      {
        if (*extension == '.') break;
        extension--;
      }
      if (extension >= fname)
      {
        *(extension++) = '\0';
        filename = g_strdup_printf ("%s-%s.%s", fname,
		     gettext (extract[extract_idx].channel_name[j]),
		     extension);
      }
      else
      {
        filename = g_strdup_printf ("%s-%s", fname,
		     gettext (extract[extract_idx].channel_name[j]));
      }

      image_ID_dst[j] = create_new_image (filename, width, height, GIMP_GRAY,
					  layer_ID_dst+j, drawable_dst+j,
					  pixel_rgn_dst+j);
      g_free (filename);
      g_free (fname);
      dst[j] = g_new (guchar, tile_height * width);
    }
  
  i = 0;
  while (i < height)
    {
      /* Get source pixel region */
      scan_lines = (i+tile_height-1 < height) ? tile_height : (height-i);
      gimp_pixel_rgn_get_rect (&pixel_rgn_src, src, 0, i, width, scan_lines);
      
      /* Extract the channel information */
      extract[extract_idx].extract_fun (src, drawable_src->bpp, scan_lines*width,
					dst);
      
      /* Set destination pixel regions */
      for (j = 0; j < num_images; j++)
	gimp_pixel_rgn_set_rect (&(pixel_rgn_dst[j]), dst[j], 0, i, width,
				 scan_lines);
      i += scan_lines;
      
      if (run_mode != GIMP_RUN_NONINTERACTIVE)
	gimp_progress_update (((gdouble)i) / (gdouble)height);
    }
  g_free (src);
  for (j = 0; j < num_images; j++)
    {
      gimp_drawable_flush (drawable_dst[j]);
      gimp_drawable_detach (drawable_dst[j]);
      g_free (dst[j]);
    }
  
  gimp_drawable_flush (drawable_src);
  gimp_drawable_detach (drawable_src);
  
  return (num_images);
}


/* Create an image. Sets layer_ID, drawable and rgn. Returns image_ID */
static gint32
create_new_image (gchar       *filename,
                  guint        width,
                  guint        height,
                  GimpImageBaseType   type,
                  gint32      *layer_ID,
                  GimpDrawable  **drawable,
                  GimpPixelRgn   *pixel_rgn)
{
  gint32 image_ID;
  GimpImageType gdtype;
  
  if (type == GIMP_GRAY) 
    gdtype = GIMP_GRAY_IMAGE;
  else if (type == GIMP_INDEXED) 
    gdtype = GIMP_INDEXED_IMAGE;
  else 
    gdtype = GIMP_RGB_IMAGE;
  
  image_ID = gimp_image_new (width, height, type);
  gimp_image_set_filename (image_ID, filename);
  
  *layer_ID = gimp_layer_new (image_ID, _("Background"), width, height,
			      gdtype, 100, GIMP_NORMAL_MODE);
  gimp_image_add_layer (image_ID, *layer_ID, 0);
  
  *drawable = gimp_drawable_get (*layer_ID);
  gimp_pixel_rgn_init (pixel_rgn, *drawable, 0, 0, (*drawable)->width,
		       (*drawable)->height, TRUE, FALSE);
  
  return (image_ID);
}


/* Extract functions */

static void 
extract_rgb (guchar  *src, 
	     gint     bpp, 
	     gint     numpix,
	     guchar **dst)
{
  register guchar *rgb_src = src;
  register guchar *red_dst = dst[0];
  register guchar *green_dst = dst[1];
  register guchar *blue_dst = dst[2];
  register gint count = numpix, offset = bpp-3;
  
  while (count-- > 0)
    {
      *(red_dst++) = *(rgb_src++);
      *(green_dst++) = *(rgb_src++);
      *(blue_dst++) = *(rgb_src++);
      rgb_src += offset;
    }
}


static void 
extract_red (guchar  *src, 
	     gint     bpp, 
	     gint     numpix,
	     guchar **dst)
{
  register guchar *rgb_src = src;
  register guchar *red_dst = dst[0];
  register gint count = numpix, offset = bpp;
  
  while (count-- > 0)
    {
      *(red_dst++) = *rgb_src;
      rgb_src += offset;
    }
}


static void 
extract_green (guchar  *src, 
	       gint     bpp, 
	       gint     numpix,
	       guchar **dst)
{
  register guchar *rgb_src = src+1;
  register guchar *green_dst = dst[0];
  register gint count = numpix, offset = bpp;
  
  while (count-- > 0)
    {
      *(green_dst++) = *rgb_src;
      rgb_src += offset;
    }
}


static void 
extract_blue (guchar  *src, 
	      gint     bpp, 
	      gint     numpix,
	      guchar **dst)
{
  register guchar *rgb_src = src+2;
  register guchar *blue_dst = dst[0];
  register gint count = numpix, offset = bpp;
  
  while (count-- > 0)
    {
      *(blue_dst++) = *rgb_src;
      rgb_src += offset;
    }
}


static void 
extract_alpha (guchar  *src, 
	       gint     bpp, 
	       gint     numpix,
	       guchar **dst)
{
  register guchar *rgb_src = src+3;
  register guchar *alpha_dst = dst[0];
  register gint count = numpix, offset = bpp;
  
  while (count-- > 0)
    {
      *(alpha_dst++) = *rgb_src;
      rgb_src += offset;
    }
}


static void
extract_cmy (guchar  *src, 
	     gint     bpp, 
	     gint     numpix,
	     guchar **dst)
{
  register guchar *rgb_src = src;
  register guchar *cyan_dst = dst[0];
  register guchar *magenta_dst = dst[1];
  register guchar *yellow_dst = dst[2];
  register gint count = numpix, offset = bpp-3;
  
  while (count-- > 0)
    {
      *(cyan_dst++) = 255 - *(rgb_src++);
      *(magenta_dst++) = 255 - *(rgb_src++);
      *(yellow_dst++) = 255 - *(rgb_src++);
      rgb_src += offset;
    }
}


static void 
extract_hsv (guchar  *src, 
	     gint     bpp, 
	     gint     numpix,
	     guchar **dst)
{
  register guchar *rgb_src = src;
  register guchar *hue_dst = dst[0];
  register guchar *sat_dst = dst[1];
  register guchar *val_dst = dst[2];
  register gint count = numpix, offset = bpp;
  gdouble hue, sat, val;
  
  while (count-- > 0)
    {
      gimp_rgb_to_hsv4 (rgb_src, &hue, &sat, &val);
      *hue_dst++ = (guchar) (hue * 255.999);
      *sat_dst++ = (guchar) (sat * 255.999);
      *val_dst++ = (guchar) (val * 255.999);
      rgb_src += offset;
    }
}


static void 
extract_hue (guchar  *src, 
	     gint     bpp, 
	     gint     numpix,
	     guchar **dst)
{
  register guchar *rgb_src = src;
  register guchar *hue_dst = dst[0];
  register gint count = numpix, offset = bpp;
  gdouble hue, dummy;
  
  while (count-- > 0)
    {
      gimp_rgb_to_hsv4 (rgb_src, &hue, &dummy, &dummy);
      *hue_dst++ = (guchar) (hue * 255.999);
      rgb_src += offset;
    }
}


static void 
extract_sat (guchar  *src, 
	     gint     bpp, 
	     gint     numpix,
	     guchar **dst)
{
  register guchar *rgb_src = src;
  register guchar *sat_dst = dst[0];
  register gint count = numpix, offset = bpp;
  gdouble sat, dummy;
  
  while (count-- > 0)
    {
      gimp_rgb_to_hsv4 (rgb_src, &dummy, &sat, &dummy);
      *sat_dst++ = (guchar) (sat * 255.999);
      rgb_src += offset;
    }
}


static void 
extract_val (guchar  *src, 
	     gint     bpp, 
	     gint     numpix,
	     guchar **dst)
{
  register guchar *rgb_src = src;
  register guchar *val_dst = dst[0];
  register gint count = numpix, offset = bpp;
  gdouble val, dummy;
  
  while (count-- > 0)
    {
      gimp_rgb_to_hsv4 (rgb_src, &dummy, &dummy, &val);
      *val_dst++ = (guchar) (val * 255.999);
      rgb_src += offset;
    }
}


static void 
extract_cyan (guchar  *src, 
	      gint     bpp, 
	      gint     numpix,
	      guchar **dst)
{
  register guchar *rgb_src = src;
  register guchar *cyan_dst = dst[0];
  register gint count = numpix, offset = bpp-1;
  
  while (count-- > 0)
    {
      *(cyan_dst++) = 255 - *(rgb_src++);
      rgb_src += offset;
    }
}


static void 
extract_magenta (guchar  *src, 
		 gint     bpp, 
		 gint     numpix,
		 guchar **dst)
{
  register guchar *rgb_src = src+1;
  register guchar *magenta_dst = dst[0];
  register gint count = numpix, offset = bpp-1;
  
  while (count-- > 0)
    {
      *(magenta_dst++) = 255 - *(rgb_src++);
      rgb_src += offset;
    }
}


static void 
extract_yellow (guchar  *src, 
		gint     bpp, 
		gint     numpix,
		guchar **dst)
{
  register guchar *rgb_src = src+2;
  register guchar *yellow_dst = dst[0];
  register gint count = numpix, offset = bpp-1;
  
  while (count-- > 0)
    {
      *(yellow_dst++) = 255 - *(rgb_src++);
      rgb_src += offset;
    }
}


static void 
extract_cmyk (guchar  *src, 
	      gint     bpp, 
	      gint     numpix,
	      guchar **dst)

{
  register guchar *rgb_src = src;
  register guchar *cyan_dst = dst[0];
  register guchar *magenta_dst = dst[1];
  register guchar *yellow_dst = dst[2];
  register guchar *black_dst = dst[3];
  register guchar k, s;
  register gint count = numpix, offset = bpp-3;
  
  while (count-- > 0)
    {
      *cyan_dst = k = 255 - *(rgb_src++);
      *magenta_dst = s = 255 - *(rgb_src++);
      if (s < k) 
	k = s;
      *yellow_dst = s = 255 - *(rgb_src++);
      if (s < k) 
	k = s;                /* Black intensity is minimum of c, m, y */
      if (k)
	{
	  *cyan_dst -= k;     /* Remove common part of c, m, y */
	  *magenta_dst -= k;
	  *yellow_dst -= k;
	}
      cyan_dst++;
      magenta_dst++;
      yellow_dst++;
      *(black_dst++) = k;
      
      rgb_src += offset;
    }
}


static void 
extract_cyank (guchar  *src, 
	       gint     bpp, 
	       gint     numpix,
	       guchar **dst)
{
  register guchar *rgb_src = src;
  register guchar *cyan_dst = dst[0];
  register guchar s, k;
  register gint count = numpix, offset = bpp-3;
  
  while (count-- > 0)
    {
      *cyan_dst = k = 255 - *(rgb_src++);
      s = 255 - *(rgb_src++);  /* magenta */
      if (s < k) k = s;
      s = 255 - *(rgb_src++);  /* yellow */
      if (s < k) k = s;
      if (k) *cyan_dst -= k;
      cyan_dst++;
      
      rgb_src += offset;
    }
}


static void 
extract_magentak (guchar  *src, 
		  gint     bpp, 
		  gint     numpix,
		  guchar **dst)
{
  register guchar *rgb_src = src;
  register guchar *magenta_dst = dst[0];
  register guchar s, k;
  register gint count = numpix, offset = bpp-3;
  
  while (count-- > 0)
    {
      k = 255 - *(rgb_src++);  /* cyan */
      *magenta_dst = s = 255 - *(rgb_src++);  /* magenta */
      if (s < k) 
	k = s;
      s = 255 - *(rgb_src++);  /* yellow */
      if (s < k) 
	k = s;
      if (k) 
	*magenta_dst -= k;
      magenta_dst++;
      
      rgb_src += offset;
    }
}


static void 
extract_yellowk (guchar  *src, 
		 gint     bpp, 
		 gint     numpix,
		 guchar **dst)

{
  register guchar *rgb_src = src;
  register guchar *yellow_dst = dst[0];
  register guchar s, k;
  register gint count = numpix, offset = bpp-3;
  
  while (count-- > 0)
    {
      k = 255 - *(rgb_src++);  /* cyan */
      s = 255 - *(rgb_src++);  /* magenta */
      if (s < k) k = s;
      *yellow_dst = s = 255 - *(rgb_src++);
      if (s < k) 
	k = s;
      if (k) 
	*yellow_dst -= k;
      yellow_dst++;
      
      rgb_src += offset;
    }
}


static gint
decompose_dialog (void)
{
  GtkWidget *dlg;
  GtkWidget *toggle;
  GtkWidget *frame;
  GtkWidget *vbox;
  GSList *group;
  gint    j;

  gimp_ui_init ("decompose", FALSE);

  dlg = gimp_dialog_new (_("Decompose"), "decompose",
			 gimp_standard_help_func, "filters/decompose.html",
			 GTK_WIN_POS_MOUSE,
			 FALSE, TRUE, FALSE,

			 GTK_STOCK_OK, decompose_ok_callback,
			 NULL, NULL, NULL, TRUE, FALSE,
			 GTK_STOCK_CANCEL, gtk_widget_destroy,
			 NULL, 1, NULL, FALSE, TRUE,

			 NULL);

  gtk_signal_connect (GTK_OBJECT (dlg), "destroy",
		      GTK_SIGNAL_FUNC (gtk_main_quit),
		      NULL);

  /*  parameter settings  */
  frame = gtk_frame_new (_("Extract Channels:"));
  gtk_frame_set_shadow_type (GTK_FRAME (frame), GTK_SHADOW_ETCHED_IN);
  gtk_container_set_border_width (GTK_CONTAINER (frame), 6);
  gtk_box_pack_start (GTK_BOX (GTK_DIALOG (dlg)->vbox), frame, TRUE, TRUE, 0);

  vbox = gtk_vbox_new (FALSE, 1);
  gtk_container_set_border_width (GTK_CONTAINER (vbox), 2);
  gtk_container_add (GTK_CONTAINER (frame), vbox);

  group = NULL;
  for (j = 0; j < NUM_EXTRACT_TYPES; j++)
    {
      if (!extract[j].dialog) 
	continue;
      toggle = gtk_radio_button_new_with_label (group, gettext (extract[j].type));
      group = gtk_radio_button_group (GTK_RADIO_BUTTON (toggle));
      gtk_box_pack_start (GTK_BOX (vbox), toggle, TRUE, TRUE, 0);
      decoint.extract_flag[j] =
	(g_strcasecmp (decovals.extract_type, extract[j].type) == 0);
      gtk_signal_connect (GTK_OBJECT (toggle), "toggled",
			  GTK_SIGNAL_FUNC (gimp_toggle_button_update),
			  &(decoint.extract_flag[j]));
      gtk_toggle_button_set_active (GTK_TOGGLE_BUTTON (toggle),
				    decoint.extract_flag[j]);
      gtk_widget_show (toggle);
    }
  gtk_widget_show (vbox);
  gtk_widget_show (frame);
  gtk_widget_show (dlg);

  gtk_main ();
  gdk_flush ();

  return decoint.run;
}

static void
decompose_ok_callback (GtkWidget *widget,
		       gpointer   data)
{
  gint j;

  decoint.run = TRUE;
  gtk_widget_destroy (GTK_WIDGET (data));

  for (j = 0; j < NUM_EXTRACT_TYPES; j++)
    {
      if (decoint.extract_flag[j])
	{
	  strcpy (decovals.extract_type, extract[j].type);
	  break;
	}
    }
}