static int F(int u, int v, short img[8][8]) {
    
    double s[8], r = 0;
    int x;
    
    for(x=0; x<8; x++) {
        
        s[x] = 
            img[x][0] * Y(0, v) +
            img[x][1] * Y(1, v) +
            img[x][2] * Y(2, v) +
            img[x][3] * Y(3, v) +
            img[x][4] * Y(4, v) +
            img[x][5] * Y(5, v) +
            img[x][6] * Y(6, v) +
            img[x][7] * Y(7, v);
    }
    
    r =	s[0] * Y(0, u) + 
    	s[1] * Y(1, u) + 
    	s[2] * Y(2, u) + 
    	s[3] * Y(3, u) + 
    	s[4] * Y(4, u) + 
    	s[5] * Y(5, u) + 
    	s[6] * Y(6, u) + 
    	s[7] * Y(7, u);
    
    return (short)(r * .25 * C(u) * C(v));
}