#include "shadow.h"

#include <math.h>

#define BLUR_RADIUS 5

#define SHADOW_OFFSET (BLUR_RADIUS * 4 / 5)

#define SHADOW_OPACITY 0.75

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 GdkPixbuf *

create_shadow (GdkPixbuf *src)

{

  int x, y, i, j;

  int width, height;

  GdkPixbuf *dest;

  static ConvFilter *filter = NULL;

  int src_rowstride, dest_rowstride;

  int src_bpp, dest_bpp;

  guchar *src_pixels, *dest_pixels;

  if (!filter)

    filter = create_blur_filter (BLUR_RADIUS);

  width = gdk_pixbuf_get_width (src) + BLUR_RADIUS * 2 + SHADOW_OFFSET;

  height = gdk_pixbuf_get_height (src) + BLUR_RADIUS * 2 + SHADOW_OFFSET;

  dest = gdk_pixbuf_new (gdk_pixbuf_get_colorspace (src),

			 gdk_pixbuf_get_has_alpha (src),

			 gdk_pixbuf_get_bits_per_sample (src),

			 width, height);

  gdk_pixbuf_fill (dest, 0);  

  src_pixels = gdk_pixbuf_get_pixels (src);

  src_rowstride = gdk_pixbuf_get_rowstride (src);

  src_bpp = gdk_pixbuf_get_has_alpha (src) ? 4 : 3;

  dest_pixels = gdk_pixbuf_get_pixels (dest);

  dest_rowstride = gdk_pixbuf_get_rowstride (dest);

  dest_bpp = gdk_pixbuf_get_has_alpha (dest) ? 4 : 3;

  for (y = 0; y < height; y++)

    {

      for (x = 0; x < width; x++)

	{

	  int sumr = 0, sumg = 0, sumb = 0, suma = 0;

	  for (i = 0; i < filter->size; i++)

	    {

	      for (j = 0; j < filter->size; j++)

		{

		  int src_x, src_y;

		  src_y = -(BLUR_RADIUS + SHADOW_OFFSET) + y - (filter->size >> 1) + i;

		  src_x = -(BLUR_RADIUS + SHADOW_OFFSET) + x - (filter->size >> 1) + j;

		  if (src_y < 0 || src_y > gdk_pixbuf_get_height (src) ||

		      src_x < 0 || src_x > gdk_pixbuf_get_width (src))

		    continue;

		  sumr += src_pixels [src_y * src_rowstride +

				      src_x * src_bpp + 0] *

		    filter->data [i * filter->size + j];

		  sumg += src_pixels [src_y * src_rowstride +

				      src_x * src_bpp + 1] * 

		    filter->data [i * filter->size + j];

		  sumb += src_pixels [src_y * src_rowstride +

				      src_x * src_bpp + 2] * 

		    filter->data [i * filter->size + j];

		  if (src_bpp == 4)

		    suma += src_pixels [src_y * src_rowstride +

					src_x * src_bpp + 3] *

		    filter->data [i * filter->size + j];

		}

	    }

	  if (dest_bpp == 4)

	    dest_pixels [y * dest_rowstride +

			 x * dest_bpp + 3] = suma * SHADOW_OPACITY;

	}

    }

  return dest;

}

GdkPixbuf *

create_shadowed_pixbuf (GdkPixbuf *src)

{

  GdkPixbuf *dest;

  dest = create_shadow (src);

  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_NEAREST, 255);

  return dest;

}