code that looks fun

-- HSL(bi-hexcone) color conversion

local abs = math.abs
local min = math.min
local tiny = -math.huge

module "color_conv"

local function max_sel(...)
	local mi, mv = -tiny
	for i,v in ipairs{...} do
		if v > mv then mi = i ; mv = v end
	end
	return mi, mv
end

function rgb2hsl(r, g, b)
	local r, g, b = r / 256, g / 256, b / 256
	local m = min(r, g, b)
	local i, M = max_sel(r, g, b)
	local C = M - m
	local l = .5 * (M + m)
	local h,s
	if C == 0 then
		h = 0
		s = 0
	else
		if i == 1 then
			h = (g-b) / C % 6
		elseif i == 2 then
			h = (b-r) / C + 2
		elseif i == 3 then
			h = (r-g) / C + 4
		end
		h = h / 6

		if l <= 1/2 then
			s = C / (2 * l)
		else
			s = C / (2 - 2 * l)
		end
	end
	return h,s,l
end

function hsl2rgb(h, s, l)
	if s == 0 then
		return l, l, l
	end

	local C
	if l <= 1/2 then
		C = 2 * l * s
	else
		C = (2 - 2 * l) * s
	end

	local h = h * 6
	local X = C * (1 - abs(h % 2 - 1))
	local m = l - .5 * C
	local r, g, b

	if h < 1 then		r = C+m ; g = X+m ; b = m
	elseif h < 2 then	g = C+m ; r = X+m ; b = m
	elseif h < 3 then	g = C+m ; b = X+m ; r = m
	elseif h < 4 then	b = C+m ; g = X+m ; r = m
	elseif h < 5 then	b = C+m ; r = X+m ; g = m
	else				r = C+m ; b = X+m ; g = m
	end

	return r * 256, g * 256, b * 256
end