public class FastBlur
{
public static Bitmap doBlur(Bitmap sentBitmap, int radius, boolean canReuseInBitmap) {
// This is a compromise between Gaussian Blur and Box blur
// 這是一個妥協(xié)于高斯模糊和方形模糊的產物
// It creates much better looking blurs than Box Blur, but is
// 他不但看上去的模糊效果比方形模糊更好，而且實現速度比高斯模糊要快
// 7x faster than my Gaussian Blur implementation.
// I called it Stack Blur because this describes best how this
// 我叫他堆棧模糊，因為他很好的闡述了過濾器是如何在內存中工作的。
// filter works internally: it creates a kind of moving stack
// of colors whilst scanning through the image. Thereby it
// 他實現了在移動顏色的棧的同時對圖片進行掃描。
// just has to add one new block of color to the right side
// 其實它只是在棧的右邊添加了一個新的顏色塊，然后移除了最左邊的顏色。
// of the stack and remove the leftmost color. The remaining
// 在棧最上層模塊的剩余顏色塊由他們所處的區(qū)域是屬于棧右邊還是左邊來決定是增加還是刪除
// 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:
// 如果你在你的代碼中使用這個算法，請?zhí)砑酉旅孢@行
// Stack Blur Algorithm by Mario Klingemann <mario@quasimondo.com>
// 堆棧模糊算法由Mario Klingemann <mario@quasimondo.com>所創(chuàng)作
Bitmap bitmap;
if (canReuseInBitmap) {
bitmap = sentBitmap;
} else {
//決定圖片像素點的存儲，即用圖片查看器看圖片屬性時候的位深參數。
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);
}
}

public class MainActivity extends AppCompatActivity {
//這個方法不會oom
/*
* 在addOnPreDrawListener中來調用blur方法是為了能夠在onCreate中獲取控件尺寸，通過scaleFactor和radius兩個參數，來控制Blur的程度。
* */
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
final ImageView imageView = (ImageView) findViewById(R.id.img);
final Bitmap bitmap = BitmapFactory.decodeResource(getResources(),
R.drawable.back1);
imageView.getViewTreeObserver().addOnPreDrawListener(
new ViewTreeObserver.OnPreDrawListener() {
@Override
public boolean onPreDraw() {
blur(bitmap, imageView);
return true;
}
});
}
private void blur(Bitmap bkg, View view) {
long startMs = System.currentTimeMillis();
float scaleFactor = 8;
float radius = 20;
Bitmap overlay = Bitmap.createBitmap(
(int) (view.getMeasuredWidth() / scaleFactor),
(int) (view.getMeasuredHeight() / scaleFactor),
Bitmap.Config.ARGB_8888);
Canvas canvas = new Canvas(overlay);
canvas.translate(-view.getLeft() / scaleFactor, -view.getTop()
/ scaleFactor);
canvas.scale(1 / scaleFactor, 1 / scaleFactor);
Paint paint = new Paint();
paint.setFlags(Paint.FILTER_BITMAP_FLAG);
canvas.drawBitmap(bkg, 0, 0, paint);
overlay = FastBlur.doBlur(overlay, (int) radius, true);
view.setBackground(new BitmapDrawable(getResources(), overlay));
}
}