Android直播室源碼圖片處理之高斯模糊，仿微信朋友圈照片模糊效果

FastBlur中，沒有對代碼做註釋，這裏簡單解釋下doBlur中三個參數的含義：

第一個：圖片資源的bitmap格式；

第二個：模糊程度（權重）——取值範圍從0開始的整數，一般不取過大的數。取值如10、15、25等，假如你傳值1000，會導致OOM錯誤；

第三個：是否可複用的bitmap。一般傳false即可。因爲可複用的bitmap對API的level有要求，level等不符合要求，會導致出錯。

看一下FastBlur的源碼：

package com.example.blur_csdn;
import android.graphics.Bitmap;
 
/**
 * Created by paveld on 3/6/14.
 * guss
 */
public class FastBlur {
 
	public static Bitmap doBlur(Bitmap sentBitmap, int radius,boolean canReuseInBitmap) 
	{
		Bitmap bitmap;
		if (canReuseInBitmap) {
			//可複用視圖
			bitmap = sentBitmap;
		} else {
			
			bitmap = sentBitmap.copy(sentBitmap.getConfig(), true);
		}
        /**
         * 權重爲0時，原樣輸出。
         * 源碼原來的判斷值時radius<1，這裏改爲以下的radius<0
         * 主要是爲了讓權重爲0時，可輸出
         */
		if (radius < 0) {
			return (null);
		}
		int w = bitmap.getWidth();
		int h = bitmap.getHeight();
		int[] pix = new int[w * h];
		bitmap.getPixels(pix, 0, w, 0, 0, w, h);
		int wm = w - 1;
		int hm = h - 1;
		int wh = w * h;
		int div = radius + radius + 1;
		int r[] = new int[wh];
		int g[] = new int[wh];
		int b[] = new int[wh];
		int rsum, gsum, bsum, x, y, i, p, yp, yi, yw;
		int vmin[] = new int[Math.max(w, h)];
		int divsum = (div + 1) >> 1;
		divsum *= divsum;
		int dv[] = new int[256 * divsum];
		for (i = 0; i < 256 * divsum; i++) {
			dv[i] = (i / divsum);
		}
		yw = yi = 0;
		int[][] stack = new int[div][3];
		int stackpointer;
		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 = pix[yi + Math.min(wm, Math.max(i, 0))];
				sir = stack[i + radius];
				sir[0] = (p & 0xff0000) >> 16;
				sir[1] = (p & 0x00ff00) >> 8;
				sir[2] = (p & 0x0000ff);
				rbs = r1 - Math.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] = Math.min(x + radius + 1, wm);
				}
				p = pix[yw + vmin[x]];
				sir[0] = (p & 0xff0000) >> 16;
				sir[1] = (p & 0x00ff00) >> 8;
				sir[2] = (p & 0x0000ff);
 
				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 = Math.max(0, yp) + x;
 
				sir = stack[i + radius];
 
				sir[0] = r[yi];
				sir[1] = g[yi];
				sir[2] = b[yi];
 
				rbs = r1 - Math.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++) {
				// Preserve alpha channel: ( 0xff000000 & pix[yi] )
				pix[yi] = (0xff000000 & pix[yi]) | (dv[rsum] << 16)
						| (dv[gsum] << 8) | 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] = Math.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;
			}
		}
		bitmap.setPixels(pix, 0, w, 0, 0, w, h);
		return (bitmap);
	}
}