/*
* Copyright © 2008 Kristian Høgsberg
* Copyright © 2009 Chris Wilson
*
* Permission to use, copy, modify, distribute, and sell this software and its
* documentation for any purpose is hereby granted without fee, provided that
* the above copyright notice appear in all copies and that both that copyright
* notice and this permission notice appear in supporting documentation, and
* that the name of the copyright holders not be used in advertising or
* publicity pertaining to distribution of the software without specific,
* written prior permission. The copyright holders make no representations
* about the suitability of this software for any purpose. It is provided "as
* is" without express or implied warranty.
*
* THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
* INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
* EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY SPECIAL, INDIRECT OR
* CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
* DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
* TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
* OF THIS SOFTWARE.
*/
#include <math.h>
#include <stdint.h>
#define ARRAY_LENGTH(a) (sizeof (a) / sizeof (a)[0])
/* Performs a simple 2D Gaussian blur of radius @radius on surface @surface. */
void
blur_image_surface (cairo_surface_t *surface, int radius)
{
cairo_surface_t *tmp;
int width, height;
int src_stride, dst_stride;
int x, y, z, w;
uint8_t *src, *dst;
uint32_t *s, *d, a, p;
int i, j, k;
uint8_t kernel[17];
const int size = ARRAY_LENGTH (kernel);
const int half = size / 2;
if (cairo_surface_status (surface))
return;
width = cairo_image_surface_get_width (surface);
height = cairo_image_surface_get_height (surface);
switch (cairo_image_surface_get_format (surface)) {
case CAIRO_FORMAT_A1:
default:
/* Don't even think about it! */
return;
case CAIRO_FORMAT_A8:
/* Handle a8 surfaces by effectively unrolling the loops by a
* factor of 4 - this is safe since we know that stride has to be a
* multiple of uint32_t. */
width /= 4;
break;
case CAIRO_FORMAT_RGB24:
case CAIRO_FORMAT_ARGB32:
break;
}
tmp = cairo_image_surface_create (CAIRO_FORMAT_ARGB32, width, height);
if (cairo_surface_status (tmp))
return;
src = cairo_image_surface_get_data (surface);
src_stride = cairo_image_surface_get_stride (surface);
dst = cairo_image_surface_get_data (tmp);
dst_stride = cairo_image_surface_get_stride (tmp);
a = 0;
for (i = 0; i < size; i++) {
double f = i - half;
a += kernel[i] = exp (- f * f / 30.0) * 80;
}
/* Horizontally blur from surface -> tmp */
for (i = 0; i < height; i++) {
s = (uint32_t *) (src + i * src_stride);
d = (uint32_t *) (dst + i * dst_stride);
for (j = 0; j < width; j++) {
if (radius < j && j < width - radius) {
d[j] = s[j];
continue;
}
x = y = z = w = 0;
for (k = 0; k < size; k++) {
if (j - half + k < 0 || j - half + k >= width)
continue;
p = s[j - half + k];
x += ((p >> 24) & 0xff) * kernel[k];
y += ((p >> 16) & 0xff) * kernel[k];
z += ((p >> 8) & 0xff) * kernel[k];
w += ((p >> 0) & 0xff) * kernel[k];
}
d[j] = (x / a << 24) | (y / a << 16) | (z / a << 8) | w / a;
}
}
/* Then vertically blur from tmp -> surface */
for (i = 0; i < height; i++) {
s = (uint32_t *) (dst + i * dst_stride);
d = (uint32_t *) (src + i * src_stride);
for (j = 0; j < width; j++) {
if (radius <= i && i < height - radius) {
d[j] = s[j];
continue;
}
x = y = z = w = 0;
for (k = 0; k < size; k++) {
if (i - half + k < 0 || i - half + k >= height)
continue;
s = (uint32_t *) (dst + (i - half + k) * dst_stride);
p = s[j];
x += ((p >> 24) & 0xff) * kernel[k];
y += ((p >> 16) & 0xff) * kernel[k];
z += ((p >> 8) & 0xff) * kernel[k];
w += ((p >> 0) & 0xff) * kernel[k];
}
d[j] = (x / a << 24) | (y / a << 16) | (z / a << 8) | w / a;
}
}
cairo_surface_destroy (tmp);
cairo_surface_mark_dirty (surface);
}
