/* screenshot-shadow.c - part of MATE Screenshot
 *
 * Copyright (C) 2001-2006  Jonathan Blandford <jrb@alum.mit.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., 51 Franklin St, Fifth Floor,
 */

/* Shadow code from anders */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include "screenshot-shadow.h"
#include <math.h>

#define BLUR_RADIUS    5
#define SHADOW_OFFSET  (BLUR_RADIUS * 4 / 5)
#define SHADOW_OPACITY 0.5

#define OUTLINE_RADIUS  1
#define OUTLINE_OFFSET  0
#define OUTLINE_OPACITY 1.0

#define dist(x0, y0, x1, y1) sqrt(((x0) - (x1))*((x0) - (x1)) + ((y0) - (y1))*((y0) - (y1)))

typedef struct {
  int size;
  double *data;
} ConvFilter;

static double
gaussian (double x, double y, double r)
{
    return ((1 / (2 * M_PI * r)) *
	    exp ((- (x * x + y * y)) / (2 * r * r)));
}

static ConvFilter *
create_blur_filter (int radius)
{
  ConvFilter *filter;
  int x, y;
  double sum;
  
  filter = g_new0 (ConvFilter, 1);
  filter->size = radius * 2 + 1;
  filter->data = g_new (double, filter->size * filter->size);

  sum = 0.0;
  
  for (y = 0 ; y < filter->size; y++)
    {
      for (x = 0 ; x < filter->size; x++)
	{
	  sum += filter->data[y * filter->size + x] = gaussian (x - (filter->size >> 1),
								y - (filter->size >> 1),
								radius);
	}
    }

  for (y = 0; y < filter->size; y++)
    {
      for (x = 0; x < filter->size; x++)
	{
	  filter->data[y * filter->size + x] /= sum;
	}
    }

  return filter;
  
}

static ConvFilter *
create_outline_filter (int radius)
{
  ConvFilter *filter;
  double *iter;
  
  filter = g_new0 (ConvFilter, 1);
  filter->size = radius * 2 + 1;
  filter->data = g_new (double, filter->size * filter->size);

  for (iter = filter->data;
       iter < filter->data + (filter->size * filter->size);
       iter++)
    {
      *iter = 1.0;
    }

  return filter;
}

static GdkPixbuf *
create_effect (GdkPixbuf *src,
               ConvFilter const *filter,
               int radius,
               int offset,
               double opacity)
{
  GdkPixbuf *dest;
  int x, y, i, j;
  int src_x, src_y;
  int suma;
  int dest_width, dest_height;
  int src_width, src_height;
  int src_rowstride, dest_rowstride;
  gboolean src_has_alpha;
  
  guchar *src_pixels, *dest_pixels;

  src_has_alpha =  gdk_pixbuf_get_has_alpha (src);

  src_width = gdk_pixbuf_get_width (src);
  src_height = gdk_pixbuf_get_height (src);
  dest_width = src_width + 2 * radius + offset;
  dest_height = src_height + 2 * radius + offset;

  dest = gdk_pixbuf_new (gdk_pixbuf_get_colorspace (src),
			 TRUE,
			 gdk_pixbuf_get_bits_per_sample (src),
			 dest_width, dest_height);
  
  gdk_pixbuf_fill (dest, 0);  
  
  src_pixels = gdk_pixbuf_get_pixels (src);
  src_rowstride = gdk_pixbuf_get_rowstride (src);
  
  dest_pixels = gdk_pixbuf_get_pixels (dest);
  dest_rowstride = gdk_pixbuf_get_rowstride (dest);
  
  for (y = 0; y < dest_height; y++)
    {
      for (x = 0; x < dest_width; x++)
	{
	  suma = 0;

	  src_x = x - radius;
	  src_y = y - radius;

	  /* We don't need to compute effect here, since this pixel will be 
	   * discarded when compositing */
	  if (src_x >= 0 && src_x < src_width &&
	      src_y >= 0 && src_y < src_height && 
	      (!src_has_alpha ||
	       src_pixels [src_y * src_rowstride + src_x * 4 + 3] == 0xFF))
	    continue;

	  for (i = 0; i < filter->size; i++)
	    {
	      for (j = 0; j < filter->size; j++)
		{
		  src_y = -(radius + offset) + y - (filter->size >> 1) + i;
		  src_x = -(radius + offset) + x - (filter->size >> 1) + j;

		  if (src_y < 0 || src_y >= src_height ||
		      src_x < 0 || src_x >= src_width)
		    continue;

		  suma += ( src_has_alpha ? 
			    src_pixels [src_y * src_rowstride + src_x * 4 + 3] :
			    0xFF ) * filter->data [i * filter->size + j];
		}
	    }

	  dest_pixels [y * dest_rowstride + x * 4 + 3] = CLAMP (suma * opacity, 0x00, 0xFF);
	}
    }
  
  return dest;
}

void
screenshot_add_shadow (GdkPixbuf **src)
{
  GdkPixbuf *dest;
  static ConvFilter *filter = NULL;
  
  if (!filter)
    filter = create_blur_filter (BLUR_RADIUS);
  
  dest = create_effect (*src, filter, 
			BLUR_RADIUS,
                        SHADOW_OFFSET, SHADOW_OPACITY);

  if (dest == NULL)
	  return;

  gdk_pixbuf_composite (*src, dest,
			BLUR_RADIUS, BLUR_RADIUS,
			gdk_pixbuf_get_width (*src),
			gdk_pixbuf_get_height (*src),
			BLUR_RADIUS, BLUR_RADIUS, 1.0, 1.0,
			GDK_INTERP_BILINEAR, 255);
  g_object_unref (*src);
  *src = dest;
}

void
screenshot_add_border (GdkPixbuf **src)
{
  GdkPixbuf *dest;
  static ConvFilter *filter = NULL;
  
  if (!filter)
    filter = create_outline_filter (OUTLINE_RADIUS);
  
  dest = create_effect (*src, filter, 
			OUTLINE_RADIUS,
                        OUTLINE_OFFSET, OUTLINE_OPACITY);

  if (dest == NULL)
	  return;

  gdk_pixbuf_composite (*src, dest,
			OUTLINE_RADIUS, OUTLINE_RADIUS,
			gdk_pixbuf_get_width (*src),
			gdk_pixbuf_get_height (*src),
			OUTLINE_RADIUS, OUTLINE_RADIUS, 1.0, 1.0,
			GDK_INTERP_BILINEAR, 255);
  g_object_unref (*src);
  *src = dest;
}