图片处理羽化效果

来源：http://www.cnblogs.com/lipeil/archive/2012/09/21/2696519.html

float mSize = 0.5f;
  public Bitmap render(Bitmap bitmap)
  {
    if(bitmap == null)return null;

    final int SIZE = 32768;
    int width = bitmap.getWidth();
    int height = bitmap.getHeight();
    int ratio = width >height ? height * SIZE /width : width * SIZE/height;//这里有额外*2^15 用于放大比率；之后的比率使用时需要右移15位，或者/2^15.

    int cx = width>>1;
    int cy = height>>1;
    int max = cx*cx + cy*cy;
    int min = (int)(max *(1-mSize));
    int diff= max -min;// ===>>    int diff = (int)(max * mSize);


    int[] pixels = new int[width * height];
    bitmap.getPixels(pixels ,0 , width , 0 , 0 , width , height);
    for(int i=0 ; i<height ; i++)
    {
      for(int j=0 ; j<width ; j++)
      {
        int pixel = pixels[i*width +j];
        int r = (pixel & 0x00ff0000)>>16;
        int g = (pixel & 0x0000ff00)>>8;
        int b = (pixel & 0x000000ff);

        int dx = cx - j;
        int dy = cy - i;

        if(width > height)
        {
          dx= (dx*ratio)>>15;
        }
        else
        {
          dy = (dy * ratio)>>15;
        }

        int dstSq = dx*dx + dy*dy;
        float v = ((float) dstSq / diff)*255;
        r = (int)(r +v);
        g = (int)(g +v);
        b = (int)(b +v);
        r = (r>255 ? 255 : (r<0? 0 : r));
        g = (g>255 ? 255 : (g<0? 0 : g));
        b = (b>255 ? 255 : (b<0? 0 : b));
        pixels[i*width +j] = (pixel & 0xff000000) + (r<<16)+ (g<<8) +b;
      }
    }

    return Bitmap.createBitmap(pixels ,width , height , Config.ARGB_8888);
  }