本文实例讲解了android 虚化图片、模糊图片、图片毛玻璃效果的实现方法，具体内容如下
效果如图：
在android可以用renderscript方便的实现这个方法：
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private void blur(bitmap bkg, view view, float radius) {
bitmap overlay = bitmap.createbitmap(view.getmeasuredwidth(), view.getmeasuredheight(), bitmap.config.argb_8888);
canvas canvas = new canvas(overlay);
canvas.drawbitmap(bkg, -view.getleft(), -view.gettop(), null);
renderscript rs = renderscript.create(this);
allocation overlayalloc = allocation.createfrombitmap(rs, overlay);
scriptintrinsicblur blur = scriptintrinsicblur.create(rs, overlayalloc.getelement());
blur.setinput(overlayalloc);
blur.setradius(radius);
blur.foreach(overlayalloc);
overlayalloc.copyto(overlay);
view.setbackground(new bitmapdrawable(getresources(), overlay));
rs.destroy();
}
但是renderscript的这个方法需要android api17，也就说需要在android 4.2上才能实现。
低于android4.2可以用java原生代码实现。但是效率会低不少：这完全是一种妥协的方式，不推荐。
/*
* this method was copied from http://stackoverflow.com/a/10028267/694378.
* the only modifications i've made are to remove a couple of log
* statements which could slow things down slightly.
*/
public bitmap fastblur(bitmap sentbitmap, int radius) {
// 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 = 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);
}
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