图像处理之快速均值模糊(Box Blur)

    public static void blur( int[] in, int[] out, int width, int height, int radius ) {
        int widthMinus1 = width-1;
        int tableSize = 2*radius+1;
        int divide[] = new int[256*tableSize];
 
        // the value scope will be 0 to 255, and number of 0 is table size
        // will get means from index not calculate result again since 
        // color value must be  between 0 and 255.
        for ( int i = 0; i < 256*tableSize; i++ )
            divide[i] = i/tableSize; 
 
        int inIndex = 0;
        
        // 
        for ( int y = 0; y < height; y++ ) {
            int outIndex = y;
            int ta = 0, tr = 0, tg = 0, tb = 0; // ARGB -> prepare for the alpha, red, green, blue color value.
 
            for ( int i = -radius; i <= radius; i++ ) {
                int rgb = in[inIndex + ImageMath.clamp(i, 0, width-1)]; // read input pixel data here. table size data.
                ta += (rgb >> 24) & 0xff;
                tr += (rgb >> 16) & 0xff;
                tg += (rgb >> 8) & 0xff;
                tb += rgb & 0xff;
            }
 
            for ( int x = 0; x < width; x++ ) { // get output pixel data.
                out[ outIndex ] = (divide[ta] << 24) | (divide[tr] << 16) | (divide[tg] << 8) | divide[tb]; // calculate the output data.
 
                int i1 = x+radius+1;
                if ( i1 > widthMinus1 )
                    i1 = widthMinus1;
                int i2 = x-radius;
                if ( i2 < 0 )
                    i2 = 0;
                int rgb1 = in[inIndex+i1];
                int rgb2 = in[inIndex+i2];
                
                ta += ((rgb1 >> 24) & 0xff)-((rgb2 >> 24) & 0xff);
                tr += ((rgb1 & 0xff0000)-(rgb2 & 0xff0000)) >> 16;
                tg += ((rgb1 & 0xff00)-(rgb2 & 0xff00)) >> 8;
                tb += (rgb1 & 0xff)-(rgb2 & 0xff);
                outIndex += height; // per column or per row as cycle...
            }
            inIndex += width; // next (i+ column number * n, n=1....n-1)
        }
    }