【转】七、android图片特效处理之光晕效果

/**
     * 光晕效果
     * @param bmp
     * @param x 光晕中心点在bmp中的x坐标
     * @param y 光晕中心点在bmp中的y坐标
     * @param r 光晕的半径
     * @return
     */
    public Bitmap halo(Bitmap bmp, int x, int y, float r)
    {
        long start = System.currentTimeMillis();
        // 高斯矩阵
        int[] gauss = new int[] { 1, 2, 1, 2, 4, 2, 1, 2, 1 };
        
        int width = bmp.getWidth();
        int height = bmp.getHeight();
        Bitmap bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.RGB_565);
        
        int pixR = 0;
        int pixG = 0;
        int pixB = 0;
        
        int pixColor = 0;
        
        int newR = 0;
        int newG = 0;
        int newB = 0;
        
        int delta = 18; // 值越小图片会越亮，越大则越暗
        
        int idx = 0;
        int[] pixels = new int[width * height];
        bmp.getPixels(pixels, 0, width, 0, 0, width, height);
        for (int i = 1, length = height - 1; i < length; i++)
        {
            for (int k = 1, len = width - 1; k < len; k++)
            {
                idx = 0;
                int distance = (int) (Math.pow(k - x, 2) + Math.pow(i - y, 2));
                // 不是中心区域的点做模糊处理
                if (distance > r * r)
                {
                    for (int m = -1; m <= 1; m++)
                    {
                        for (int n = -1; n <= 1; n++)
                        {
                            pixColor = pixels[(i + m) * width + k + n];
                            pixR = Color.red(pixColor);
                            pixG = Color.green(pixColor);
                            pixB = Color.blue(pixColor);
                            
                            newR = newR + (int) (pixR * gauss[idx]);
                            newG = newG + (int) (pixG * gauss[idx]);
                            newB = newB + (int) (pixB * gauss[idx]);
                            idx++;
                        }
                    }
                    
                    newR /= delta;
                    newG /= delta;
                    newB /= delta;
                    
                    newR = Math.min(255, Math.max(0, newR));
                    newG = Math.min(255, Math.max(0, newG));
                    newB = Math.min(255, Math.max(0, newB));
                    
                    pixels[i * width + k] = Color.argb(255, newR, newG, newB);
                    
                    newR = 0;
                    newG = 0;
                    newB = 0;
                }
            }
        }
        
        bitmap.setPixels(pixels, 0, width, 0, 0, width, height);
        long end = System.currentTimeMillis();
        Log.d("may", "used time="+(end - start));
        return bitmap;
    }