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95 lines
3.4 KiB
95 lines
3.4 KiB
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/*
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* Copyright © 2008 Kristian Høgsberg
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* Copyright © 2009 Chris Wilson
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*
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* Permission to use, copy, modify, distribute, and sell this software and its
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* documentation for any purpose is hereby granted without fee, provided that
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* the above copyright notice appear in all copies and that both that copyright
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* notice and this permission notice appear in supporting documentation, and
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* that the name of the copyright holders not be used in advertising or
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* publicity pertaining to distribution of the software without specific,
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* written prior permission. The copyright holders make no representations
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* about the suitability of this software for any purpose. It is provided "as
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* is" without express or implied warranty.
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*
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* THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
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* INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
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* EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY SPECIAL, INDIRECT OR
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* CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
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* DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
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* TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
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* OF THIS SOFTWARE.
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*/
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#include <math.h>
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#include <memory.h>
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#include <stdint.h>
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#include <stdlib.h>
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#include <cairo.h>
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#include "canvas.h"
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void
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Canvas::blur(cairo_surface_t *surface, int radius) {
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// Steve Hanov, 2009
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// Released into the public domain.
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// get width, height
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int width = cairo_image_surface_get_width( surface );
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int height = cairo_image_surface_get_height( surface );
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unsigned char* dst = (unsigned char*)malloc(width*height*4);
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unsigned* precalc =
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(unsigned*)malloc(width*height*sizeof(unsigned));
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unsigned char* src = cairo_image_surface_get_data( surface );
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double mul=1.f/((radius*2)*(radius*2));
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int channel;
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// The number of times to perform the averaging. According to wikipedia,
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// three iterations is good enough to pass for a gaussian.
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const int MAX_ITERATIONS = 3;
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int iteration;
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memcpy( dst, src, width*height*4 );
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for ( iteration = 0; iteration < MAX_ITERATIONS; iteration++ ) {
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for( channel = 0; channel < 4; channel++ ) {
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int x,y;
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// precomputation step.
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unsigned char* pix = src;
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unsigned* pre = precalc;
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pix += channel;
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for (y=0;y<height;y++) {
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for (x=0;x<width;x++) {
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int tot=pix[0];
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if (x>0) tot+=pre[-1];
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if (y>0) tot+=pre[-width];
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if (x>0 && y>0) tot-=pre[-width-1];
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*pre++=tot;
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pix += 4;
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}
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}
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// blur step.
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pix = dst + (int)radius * width * 4 + (int)radius * 4 + channel;
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for (y=radius;y<height-radius;y++) {
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for (x=radius;x<width-radius;x++) {
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int l = x < radius ? 0 : x - radius;
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int t = y < radius ? 0 : y - radius;
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int r = x + radius >= width ? width - 1 : x + radius;
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int b = y + radius >= height ? height - 1 : y + radius;
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int tot = precalc[r+b*width] + precalc[l+t*width] -
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precalc[l+b*width] - precalc[r+t*width];
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*pix=(unsigned char)(tot*mul);
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pix += 4;
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}
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pix += (int)radius * 2 * 4;
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}
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}
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memcpy( src, dst, width*height*4 );
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}
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free( dst );
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free( precalc );
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}
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