快速堆栈模糊算法

上一篇快速高斯模糊的原作者也有另一个比较快速的模糊算法Stack Blur,字面意思为堆栈模糊。

源地址为：http://incubator.quasimondo.com/processing/fast_blur_deluxe.php

这个算法在多个平台上都有实现，安卓以及IOS，JS等。

processing源码:http://incubator.quasimondo.com/processing/stackblur.pde
 
效果图:

转为C语言实现版本。
 
代码如下:

+ View Code?

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// Stack Blur v1.0 // // Author: Mario Klingemann <mario@quasimondo.com> // http://incubator.quasimondo.com // created Feburary 29, 2004 // C version updated and performance optimization by tntmonks(http://tntmonks.cnblogs.com)   // This is a compromise between Gaussian Blur and Box blur // It creates much better looking blurs than Box Blur, but is // 7x faster than my Gaussian Blur implementation. // // I called it Stack Blur because this describes best how this // filter works internally: it creates a kind of moving stack // of colors whilst scanning through the image. Thereby it // just has to add one new block of color to the right side // of the stack and remove the leftmost color. The remaining // colors on the topmost layer of the stack are either added on // or reduced by one, depending on if they are on the right or // on the left side of the stack. // // If you are using this algorithm in your code please add // the following line: // // Stack Blur Algorithm by Mario Klingemann <mario@quasimondo.com>   #define MAX(x,y) (x>y?x:y) #define MIN(x,y) (x>y?y:x) void fastStackBlur(unsigned char* pix, unsigned int w, unsigned int h, unsigned int comp, int radius) {     unsigned int wm = w - 1;     unsigned int hm = h - 1;     unsigned int imageSize = w * h;     unsigned int div = radius + radius + 1;       unsigned char * rgb = (unsigned char *)malloc(sizeof(unsigned char) * imageSize * 3);     unsigned char * r = rgb;     unsigned char * g = rgb + imageSize;     unsigned char * b = rgb + imageSize * 2;     int rsum, gsum, bsum, x, y, i, p, yp, yi, yw;       unsigned int *vmin = (unsigned int *)malloc(MAX(w, h) * sizeof(unsigned int));       int divsum = (div + 1) >> 1;     divsum *= divsum;     int *dv = (int *)malloc(256 * divsum * sizeof(int));     for (i = 0; i < 256 * divsum; i++) {         dv[i] = (i / divsum);     }       yw = yi = 0;       int(*stack)[3] = (int(*)[3])malloc(div * 3 * sizeof(int));     unsigned int stackpointer;     unsigned int stackstart;     int *sir;     int rbs;     int r1 = radius + 1;     int routsum, goutsum, boutsum;     int rinsum, ginsum, binsum;       for (y = 0; y < h; y++) {         rinsum = ginsum = binsum = routsum = goutsum = boutsum = rsum = gsum = bsum = 0;         for (i = -radius; i <= radius; i++) {             p = yi + (MIN(wm, MAX(i, 0)));             sir = stack[i + radius];             sir[0] = pix[(p*comp)];             sir[1] = pix[(p*comp) + 1];             sir[2] = pix[(p*comp) + 2];               rbs = r1 - abs(i);             rsum += sir[0] * rbs;             gsum += sir[1] * rbs;             bsum += sir[2] * rbs;             if (i > 0) {                 rinsum += sir[0];                 ginsum += sir[1];                 binsum += sir[2];             }             else {                 routsum += sir[0];                 goutsum += sir[1];                 boutsum += sir[2];             }         }         stackpointer = radius;           for (x = 0; x < w; x++) {               r[yi] = dv[rsum];             g[yi] = dv[gsum];             b[yi] = dv[bsum];               rsum -= routsum;             gsum -= goutsum;             bsum -= boutsum;               stackstart = stackpointer - radius + div;             sir = stack[stackstart % div];               routsum -= sir[0];             goutsum -= sir[1];             boutsum -= sir[2];               if (y == 0) {                 vmin[x] = MIN(x + radius + 1, wm);             }             p = yw + vmin[x];                 sir[0] = pix[(p*comp)];             sir[1] = pix[(p*comp) + 1];             sir[2] = pix[(p*comp) + 2];             rinsum += sir[0];             ginsum += sir[1];             binsum += sir[2];               rsum += rinsum;             gsum += ginsum;             bsum += binsum;               stackpointer = (stackpointer + 1) % div;             sir = stack[(stackpointer) % div];               routsum += sir[0];             goutsum += sir[1];             boutsum += sir[2];               rinsum -= sir[0];             ginsum -= sir[1];             binsum -= sir[2];               yi++;         }         yw += w;     }     for (x = 0; x < w; x++) {         rinsum = ginsum = binsum = routsum = goutsum = boutsum = rsum = gsum = bsum = 0;         yp = -radius * w;         for (i = -radius; i <= radius; i++) {             yi = MAX(0, yp) + x;               sir = stack[i + radius];               sir[0] = r[yi];             sir[1] = g[yi];             sir[2] = b[yi];               rbs = r1 - abs(i);               rsum += r[yi] * rbs;             gsum += g[yi] * rbs;             bsum += b[yi] * rbs;               if (i > 0) {                 rinsum += sir[0];                 ginsum += sir[1];                 binsum += sir[2];             }             else {                 routsum += sir[0];                 goutsum += sir[1];                 boutsum += sir[2];             }               if (i < hm) {                 yp += w;             }         }         yi = x;         stackpointer = radius;         for (y = 0; y < h; y++) {               pix[(yi*comp)] = dv[rsum];             pix[(yi*comp) + 1] = dv[gsum];             pix[(yi*comp) + 2] = dv[bsum];             rsum -= routsum;             gsum -= goutsum;             bsum -= boutsum;               stackstart = stackpointer - radius + div;             sir = stack[stackstart % div];               routsum -= sir[0];             goutsum -= sir[1];             boutsum -= sir[2];               if (x == 0) {                 vmin[y] = MIN(y + r1, hm) * w;             }             p = x + vmin[y];               sir[0] = r[p];             sir[1] = g[p];             sir[2] = b[p];               rinsum += sir[0];             ginsum += sir[1];             binsum += sir[2];               rsum += rinsum;             gsum += ginsum;             bsum += binsum;               stackpointer = (stackpointer + 1) % div;             sir = stack[stackpointer];               routsum += sir[0];             goutsum += sir[1];             boutsum += sir[2];               rinsum -= sir[0];             ginsum -= sir[1];             binsum -= sir[2];               yi += w;         }     }       free(rgb);     free(vmin);     free(dv);     free(stack); }

　　在博主机子上测试一张5000x3000的图像，模糊半径为10的情况下，耗时1s.