-- 0-255, 0-255, 0-255, [0-1]
function rgb(r,g,b,a)
    a = (a or 1) * 255
    a = a + 0.5 - (a + 0.5) % 1
    return ((r&0x0ff)<<0x00)|((g&0x0ff)<<0x08)|((b&0x0ff)<<0x10)|((a&0x0ff)<<0x18)
end