lib/color.lua

local hexadecimal, rgb, hex, index
local pairs, tonumber = pairs, tonumber
local string_len, math_fmod, math_floor = string.len, math.fmod, math.floor

local list = {}
for i = 1, string_len("0123456789ABCDEF") do
    list[i - 1] = string.sub("0123456789ABCDEF", i, i)
end

local Color_Cache = {}

return function(r, g, b)
    rgb = {r, g, b}

    if Color_Cache[rgb] then
        return Color_Cache[rgb]
    end

    hexadecimal = "0x"

    for _, value in ipairs(rgb) do
        hex = ""

        while value > 0 do
            index = math_fmod(value, 16)
            value = math_floor(value / 16)
            hex = list[index] .. hex
        end

        if string_len(hex) == 0 then
            hex = "00"

        elseif string_len(hex) == 1 then
            hex = "0".. hex
        end

        hexadecimal = hexadecimal .. hex
    end

    Color_Cache[rgb] = tonumber(hexadecimal)
    return Color_Cache[rgb]
end