You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
72 lines
2.2 KiB
72 lines
2.2 KiB
|
|
#include <math.h>
|
|
#include <memory.h>
|
|
#include <stdint.h>
|
|
#include <stdlib.h>
|
|
#include <cairo.h>
|
|
#include "canvas.h"
|
|
|
|
void
|
|
Canvas::blur(cairo_surface_t *surface, int radius) {
|
|
// Steve Hanov, 2009
|
|
// Released into the public domain.
|
|
|
|
// get width, height
|
|
int width = cairo_image_surface_get_width( surface );
|
|
int height = cairo_image_surface_get_height( surface );
|
|
unsigned char* dst = (unsigned char*)malloc(width*height*4);
|
|
unsigned* precalc =
|
|
(unsigned*)malloc(width*height*sizeof(unsigned));
|
|
unsigned char* src = cairo_image_surface_get_data( surface );
|
|
double mul=1.f/((radius*2)*(radius*2));
|
|
int channel;
|
|
|
|
// The number of times to perform the averaging. According to wikipedia,
|
|
// three iterations is good enough to pass for a gaussian.
|
|
const int MAX_ITERATIONS = 3;
|
|
int iteration;
|
|
|
|
memcpy( dst, src, width*height*4 );
|
|
|
|
for ( iteration = 0; iteration < MAX_ITERATIONS; iteration++ ) {
|
|
for( channel = 0; channel < 4; channel++ ) {
|
|
int x,y;
|
|
|
|
// precomputation step.
|
|
unsigned char* pix = src;
|
|
unsigned* pre = precalc;
|
|
|
|
pix += channel;
|
|
for (y=0;y<height;y++) {
|
|
for (x=0;x<width;x++) {
|
|
int tot=pix[0];
|
|
if (x>0) tot+=pre[-1];
|
|
if (y>0) tot+=pre[-width];
|
|
if (x>0 && y>0) tot-=pre[-width-1];
|
|
*pre++=tot;
|
|
pix += 4;
|
|
}
|
|
}
|
|
|
|
// blur step.
|
|
pix = dst + (int)radius * width * 4 + (int)radius * 4 + channel;
|
|
for (y=radius;y<height-radius;y++) {
|
|
for (x=radius;x<width-radius;x++) {
|
|
int l = x < radius ? 0 : x - radius;
|
|
int t = y < radius ? 0 : y - radius;
|
|
int r = x + radius >= width ? width - 1 : x + radius;
|
|
int b = y + radius >= height ? height - 1 : y + radius;
|
|
int tot = precalc[r+b*width] + precalc[l+t*width] -
|
|
precalc[l+b*width] - precalc[r+t*width];
|
|
*pix=(unsigned char)(tot*mul);
|
|
pix += 4;
|
|
}
|
|
pix += (int)radius * 2 * 4;
|
|
}
|
|
}
|
|
memcpy( src, dst, width*height*4 );
|
|
}
|
|
|
|
free( dst );
|
|
free( precalc );
|
|
}
|