-- 0-255, 0-255, 0-255, 0-100
function rgba(R, G, B, A)
    A = A or 100
    A = A + 0.5 - (A + 0.5) % 1
    return ((R&0x0ff)<<0x00)|((G&0x0ff)<<0x08)|((B&0x0ff)<<0x10)|((A&0x0ff)<<0x18)
end