void  resizeBilinearGray(uint8_t *pixels, uint8_t *temp, int w, int h, int w2, int h2) {

    int A, B, C, D, x, y, index, gray ;
    float x_ratio = ((float)(w-1))/w2 ;
    float y_ratio = ((float)(h-1))/h2 ;
    float x_diff, y_diff;
    int offset = 0 ;

    for (int i=0;i<h2;i++) {
        for (int j=0;j<w2;j++) {
            x = (int)(x_ratio * j) ;
            y = (int)(y_ratio * i) ;
            x_diff = (x_ratio * j) - x ;
            y_diff = (y_ratio * i) - y ;
            index = y*w+x ;

            // range is 0 to 255 thus bitwise AND with 0xff
            A = pixels[index] & 0xff ;
            B = pixels[index+1] & 0xff ;
            C = pixels[index+w] & 0xff ;
            D = pixels[index+w+1] & 0xff ;

            // Y = A(1-w)(1-h) + B(w)(1-h) + C(h)(1-w) + Dwh
            gray = (int)(
                        A*(1-x_diff)*(1-y_diff) +  B*(x_diff)*(1-y_diff) +
                        C*(y_diff)*(1-x_diff)   +  D*(x_diff*y_diff)
                        ) ;

            temp[offset++] = gray ;
        }
    }