/* 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.
 */

/* This plugin by thorsten@arch.usyd.edu.au.
 * Based on S&P's Gauss and Laplace filters.
 */

#include "config.h"

#include <stdlib.h>

#include <libgimp/gimp.h>

#include "libgimp/stdplugins-intl.h"


#define PLUG_IN_PROC   "plug-in-laplace"
#define PLUG_IN_BINARY "laplace"


/* 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   laplace             (GimpDrawable *drawable);
static void   laplace_prepare_row (GimpPixelRgn *pixel_rgn,
                                   guchar       *data,
                                   gint          x,
                                   gint          y,
                                   gint          w);


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


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_install_procedure (PLUG_IN_PROC,
			  "Edge Detection with Laplace Operation",
			  "This plugin creates one-pixel wide edges from the "
			  "image, with the value proportional to the gradient. "
			  "It uses the Laplace operator (a 3x3 kernel with -8 "
			  "in the middle). The image has to be laplacered to "
			  "get useful results, a gauss_iir with 1.5 - 5.0 "
			  "depending on the noise in the image is best.",
			  "Thorsten Schnier",
			  "Thorsten Schnier",
			  "1997",
			  N_("_Laplace"),
			  "RGB*, GRAY*",
			  GIMP_PLUGIN,
			  G_N_ELEMENTS (args), 0,
			  args, NULL);

  gimp_plugin_menu_register (PLUG_IN_PROC, "<Image>/Filters/Edge-Detect");
}

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

  run_mode = param[0].data.d_int32;

  INIT_I18N();

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

  /*  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_tile_cache_ntiles (2 * (drawable->width / gimp_tile_width () + 1));
      laplace (drawable);

      if (run_mode != GIMP_RUN_NONINTERACTIVE)
	gimp_displays_flush ();
    }
  else
    {
      /* gimp_message ("laplace: 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
laplace_prepare_row (GimpPixelRgn *pixel_rgn,
		     guchar       *data,
		     gint          x,
		     gint          y,
		     gint          w)
{
  gint bpp = pixel_rgn->bpp;
  gint b;

  if (y < 0)
    {
      gimp_pixel_rgn_get_row (pixel_rgn, data, x, (y + 1), w);
    }
  else if (y == pixel_rgn->h)
    {
      gimp_pixel_rgn_get_row (pixel_rgn, data, x, (y - 1), w);
    }
  else
    {
      gimp_pixel_rgn_get_row (pixel_rgn, data, x, y, w);
    }

  /*  Fill in edge pixels  */
  for (b = 0; b < bpp; b++)
    {
      data[b - bpp] = data[b];
      data[w * bpp + b] = data[(w - 1) * bpp + b];
    }
}

#define SIGN(a) (((a) > 0) ? 1 : -1)
#define RMS(a,b) (sqrt (pow ((a),2) + pow ((b), 2)))
#define BLACK_REGION(val) ((val) > 128)
#define WHITE_REGION(val) ((val) <= 128)

static void
minmax  (gint  x1,
	 gint  x2,
	 gint  x3,
	 gint  x4,
	 gint  x5,
	 gint *min_result,
	 gint *max_result)
{
  gint min1, min2, max1, max2;

  if (x1 > x2)
    {
      max1 = x1;
      min1 = x2;
    }
  else
    {
      max1 = x2;
      min1 = x1;
    }

  if (x3 > x4)
    {
      max2 = x3;
      min2 = x4;
    }
  else
    {
      max2 = x4;
      min2 = x3;
    }

  if (min1 < min2)
    *min_result = MIN (min1, x5);
  else
    *min_result = MIN (min2, x5);

  if (max1 > max2)
    *max_result = MAX (max1, x5);
  else
    *max_result = MAX (max2, x5);
}

static void
laplace (GimpDrawable *drawable)
{
  GimpPixelRgn srcPR, destPR;
  gint         width, height;
  gint         bytes;
  gint         current;
  gint         gradient;
  gint         alpha;
  gint         counter;
  guchar      *dest, *d;
  guchar      *prev_row, *pr;
  guchar      *cur_row, *cr;
  guchar      *next_row, *nr;
  guchar      *tmp;
  gint         row, col;
  gint         x1, y1, x2, y2;
  gint         minval, maxval;

  /* Get the input area. This is the bounding box of the selection in
   *  the image (or the entire image if there is no selection). Only
   *  operating on the input area is simply an optimization. It doesn't
   *  need to be done for correct operation. (It simply makes it go
   *  faster, since fewer pixels need to be operated on).
   */

  gimp_drawable_mask_bounds (drawable->drawable_id, &x1, &y1, &x2, &y2);
  gimp_progress_init (_("Laplace"));

  /* Get the size of the input image. (This will/must be the same
   *  as the size of the output image.
   */
  width  = drawable->width;
  height = drawable->height;
  bytes  = drawable->bpp;
  alpha  = gimp_drawable_has_alpha (drawable->drawable_id);

  /*  allocate row buffers  */
  prev_row = g_new (guchar, (x2 - x1 + 2) * bytes);
  cur_row  = g_new (guchar, (x2 - x1 + 2) * bytes);
  next_row = g_new (guchar, (x2 - x1 + 2) * bytes);
  dest     = g_new (guchar, (x2 - x1) * bytes);

  /*  initialize the pixel regions  */
  gimp_pixel_rgn_init (&srcPR, drawable, 0, 0, width, height, FALSE, FALSE);
  gimp_pixel_rgn_init (&destPR, drawable, 0, 0, width, height, TRUE, TRUE);

  pr = prev_row + bytes;
  cr = cur_row + bytes;
  nr = next_row + bytes;

  laplace_prepare_row (&srcPR, pr, x1, y1 - 1, (x2 - x1));
  laplace_prepare_row (&srcPR, cr, x1, y1, (x2 - x1));

  /*  loop through the rows, applying the laplace convolution  */
  for (row = y1; row < y2; row++)
    {
      /*  prepare the next row  */
      laplace_prepare_row (&srcPR, nr, x1, row + 1, (x2 - x1));

      d = dest;
      for (col = 0; col < (x2 - x1) * bytes; col++)
	if (alpha && (((col + 1) % bytes) == 0)) /* the alpha channel */
          {
            *d++ = cr[col];
          }
	else
	  {
	    minmax (pr[col], cr[col - bytes], cr[col], cr[col + bytes],
		    nr[col], &minval, &maxval); /* four-neighbourhood */

	    gradient = (0.5 * MAX ((maxval - cr [col]), (cr[col]- minval)));

	    *d++ = (((pr[col - bytes] + pr[col]       + pr[col + bytes] +
                      cr[col - bytes] - (8 * cr[col]) + cr[col + bytes] +
                      nr[col - bytes] + nr[col]       + nr[col + bytes]) > 0) ?
                    gradient : (128 + gradient));
	  }

      /*  store the dest  */
      gimp_pixel_rgn_set_row (&destPR, dest, x1, row, (x2 - x1));

      /*  shuffle the row pointers  */
      tmp = pr;
      pr = cr;
      cr = nr;
      nr = tmp;

      if ((row % 20) == 0)
	gimp_progress_update ((gdouble) row / (gdouble) (y2 - y1));
    }


  /* now clean up: leave only edges, but keep gradient value */


  gimp_pixel_rgn_init (&srcPR, drawable, 0, 0, width, height, FALSE, TRUE);

  pr = prev_row + bytes;
  cr = cur_row + bytes;
  nr = next_row + bytes;

  laplace_prepare_row (&srcPR, pr, x1, y1 - 1, (x2 - x1));
  laplace_prepare_row (&srcPR, cr, x1, y1, (x2 - x1));

  gimp_progress_init (_("Cleanup"));
  counter =0;

  /*  loop through the rows, applying the laplace convolution  */
  for (row = y1; row < y2; row++)
    {
      /*  prepare the next row  */
      laplace_prepare_row (&srcPR, nr, x1, row + 1, (x2 - x1));

      d = dest;
      for (col = 0; col < (x2 - x1) * bytes; col++)
        {
          current = cr[col];
          current = ((WHITE_REGION (current) &&
                      (BLACK_REGION (pr[col - bytes]) ||
                       BLACK_REGION (pr[col])         ||
                       BLACK_REGION (pr[col + bytes]) ||
                       BLACK_REGION (cr[col - bytes]) ||
                       BLACK_REGION (cr[col + bytes]) ||
                       BLACK_REGION (nr[col - bytes]) ||
                       BLACK_REGION (nr[col])         ||
                       BLACK_REGION (nr[col + bytes]))) ?
                     ((current >= 128) ? (current - 128) : current) : 0);

          if (alpha && (((col + 1) % bytes) == 0)) /* the alpha channel */
            {
              *d++ = (counter == 0) ? 0 : 255;
              counter = 0;
            }
          else
            {
              *d++ = current;

              if (current > 15)
                counter ++;
            }
        }

      /*  store the dest  */
      gimp_pixel_rgn_set_row (&destPR, dest, x1, row, (x2 - x1));

      /*  shuffle the row pointers  */
      tmp = pr;
      pr = cr;
      cr = nr;
      nr = tmp;

      if ((row % 20) == 0)
	gimp_progress_update ((gdouble) row / (gdouble) (y2 - y1));
    }

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

  g_free (prev_row);
  g_free (cur_row);
  g_free (next_row);
  g_free (dest);
}