【Android高级】高斯模糊效果从319ms到3ms的优化实现

       以前做一个旅游app项目的时候，当时有个项目需求就是首页菜单栏背景是用高斯模糊效果实现的，当时手头其他事情多的不得了，为了赶上进度，直接要求美工把原图的部分区域P成了高斯模糊效果，23333333。。。这样的屏幕适配简直是坨屎，后面项目完了也没有太在意这个问题，后面面试的时候居然问答这块的问题了，2333333。。。

       于是最近有空在研究图像的高斯模糊的处理实现了。

       我要做的效果就是自定义image大小，自定义高斯模糊的区域，这样才算我要的效果。

       先上图分别是优化前和优化后的，大家可想这个优化的作用多么巨大，我直接把这个效果的显示耗时在界面绘制出来了,下面图片中的单位打错了额，是ms。

3ms VS 209ms

4ms VS 197ms

       说下实现吧，那个算法我就没有怎么研究了，直接是个算法类，直接把要模糊的Bitmap传进去返回的就是模糊后的。代码如下：

public class FastBlur {public static Bitmap doBlur(Bitmap sentBitmap, int radius, boolean canReuseInBitmap) {// Stack Blur v1.0 from// http://www.quasimondo.com/StackBlurForCanvas/StackBlurDemo.html//// Java Author: Mario Klingemann <mario at="" quasimondo.com="">// http://incubator.quasimondo.com// created Feburary 29, 2004// Android port : Yahel Bouaziz <yahel at="" kayenko.com="">// http://www.kayenko.com// ported april 5th, 2012// 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>Bitmap bitmap;if (canReuseInBitmap) {bitmap = sentBitmap;} else {bitmap = sentBitmap.copy(sentBitmap.getConfig(), true);}if (radius < 1) {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);}
}

        先上优化前的方法：因为下面红字部分那句的代码把我坑惨了，原来用了matrix，在新建的时候还是要用matrix前的大小，我也是晕的不要不要的了。。。

       还有注意要根据演示区域的大小，缩放bitmap的大小后再剪裁，再模糊。

       这里顺便熟悉了canvas，drawBitmap，放大缩小的一些方法

public void test(View v) {Bitmap srcbitmap = BitmapFactory.decodeResource(getResources(),R.drawable.meitu);long t1 = System.currentTimeMillis();imageView.setBackground(new BitmapDrawable(getResources(), srcbitmap));// 设置大背景Bitmap backBitmap = Bitmap.createBitmap(textView.getMeasuredWidth(),// 设置需高斯模糊的背景textView.getMeasuredHeight(), Config.RGB_565);float f1 = (float) imageView.getMeasuredWidth()/ (float) srcbitmap.getWidth();float f2 = (float) imageView.getMeasuredHeight()/ (float) srcbitmap.getHeight();Matrix matrix = new Matrix();matrix.postScale(f1, f2);Bitmap desBitmap = Bitmap.createBitmap(srcbitmap, 0, 0,srcbitmap.getWidth(), srcbitmap.getHeight(), matrix, true); <span style="color:#ff0000;">因为作为背景的bmp已经缩放，那么需要剪裁的bmp也要缩放----------这里3/4参数是坑</span>Bitmap lastBitmap = Bitmap.createBitmap(desBitmap, textView.getLeft(),textView.getTop(), textView.getMeasuredWidth(),textView.getMeasuredHeight()); // 根据模糊的区域剪裁Canvas canvas = new Canvas(backBitmap);canvas.drawBitmap(lastBitmap, 0, 0, new Paint());backBitmap = FastBlur.doBlur(backBitmap, (int) 20, true);textView.setBackground(new BitmapDrawable(getResources(), backBitmap));long t2 = System.currentTimeMillis();textView.setText((t2 - t1) + "S");// 319S}

其实现原理是反正效果也是模糊的，先把图片弄小模糊，再把模糊放大，这样就减少了算法的复杂度

public void test2(View v) {int rad = 8;Bitmap srcbitmap = BitmapFactory.decodeResource(getResources(),R.drawable.meitu);long t1 = System.currentTimeMillis();imageView.setBackground(new BitmapDrawable(getResources(), srcbitmap));// 设置大背景Bitmap backBitmap = Bitmap.createBitmap(textView.getMeasuredWidth()/rad,// 设置需高斯模糊的背景textView.getMeasuredHeight()/rad, Config.RGB_565);float f1 = (float) imageView.getMeasuredWidth()/ (float) srcbitmap.getWidth();float f2 = (float) imageView.getMeasuredHeight()/ (float) srcbitmap.getHeight();Matrix matrix = new Matrix();matrix.postScale(f1/8, f2/8);Bitmap desBitmap = Bitmap.createBitmap(srcbitmap, 0, 0,srcbitmap.getWidth(), srcbitmap.getHeight(), matrix, true); // 因为作为背景的bmp已经缩放，那么需要剪裁的bmp也要缩放----------这里3/4参数是坑Bitmap lastBitmap = Bitmap.createBitmap(desBitmap, textView.getLeft()/8,textView.getTop()/8, textView.getMeasuredWidth()/8,textView.getMeasuredHeight()/8); // 根据模糊的区域剪裁Canvas canvas = new Canvas(backBitmap);canvas.drawBitmap(lastBitmap, 0, 0, new Paint());backBitmap = FastBlur.doBlur(backBitmap, (int) 2, true);canvas.scale(1/rad, 1/rad);textView.setBackground(new BitmapDrawable(getResources(), backBitmap));long t2 = System.currentTimeMillis();textView.setText((t2 - t1) + "S");// 2S}