Android中实现布局背景模糊化处理的方法

在模仿 IOS 密码输入页面的时候发现其背景有模糊处理,于是了解了一下并记录下来,以便使用.在Android 中具体实现方法如下
查考 http://www.jb51.net/article/64781.htm

private void applyBlur() {  

  // 获取壁纸管理器
  WallpaperManager wallpaperManager = WallpaperManager.getInstance(this.getContext());
  // 获取当前壁纸
  Drawable wallpaperDrawable = wallpaperManager.getDrawable();
  // 将Drawable,转成Bitmap
  Bitmap bmp = ((BitmapDrawable) wallpaperDrawable).getBitmap();  

  blur(bmp);
}  

下面之所以要进行small 和big的处理,是因为仅仅靠ScriptIntrinsicBlur  来处理模式,不能到达更模式的效果,如果需要加深模式效果就需要先把背景图片缩小,在处理完之后再放大.这个可以使用Matrix 来实现,而且这样可以缩短模糊化得时间

@TargetApi(Build.VERSION_CODES.JELLY_BEAN_MR1)
private void blur(Bitmap bkg) {
  long startMs = System.currentTimeMillis();
  float radius = 20;  

  bkg = small(bkg);
  Bitmap bitmap = bkg.copy(bkg.getConfig(), true); 

  final RenderScript rs = RenderScript.create(this.getContext());
  final Allocation input = Allocation.createFromBitmap(rs, bkg, Allocation.MipmapControl.MIPMAP_NONE,
      Allocation.USAGE_SCRIPT);
  final Allocation output = Allocation.createTyped(rs, input.getType());
  final ScriptIntrinsicBlur script = ScriptIntrinsicBlur.create(rs, Element.U8_4(rs));
  script.setRadius(radius);
  script.setInput(input);
  script.forEach(output);
  output.copyTo(bitmap); 

  bitmap = big(bitmap);
  setBackground(new BitmapDrawable(getResources(), bitmap));
  rs.destroy();
  Log.d("zhangle","blur take away:" + (System.currentTimeMillis() - startMs )+ "ms");
}  

private static Bitmap big(Bitmap bitmap) {
   Matrix matrix = new Matrix();
   matrix.postScale(4f,4f); //长和宽放大缩小的比例
   Bitmap resizeBmp = Bitmap.createBitmap(bitmap,0,0,bitmap.getWidth(),bitmap.getHeight(),matrix,true);
   return resizeBmp;
 } 

 private static Bitmap small(Bitmap bitmap) {
   Matrix matrix = new Matrix();
   matrix.postScale(0.25f,0.25f); //长和宽放大缩小的比例
   Bitmap resizeBmp = Bitmap.createBitmap(bitmap,0,0,bitmap.getWidth(),bitmap.getHeight(),matrix,true);
   return resizeBmp;
}