Module:Color

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-- Introduction: https://colorspace.r-forge.r-project.org/articles/color_spaces.html

local p = {}

local function isempty(v)
	return v == nil or v == ''
end

local function hexToRgb(color)
	local cleanColor = color:gsub("#", "#"):match('^[%s#]*(.-)[%s;]*$')
	if (#cleanColor == 6) then
		return {
			r = tonumber(string.sub(cleanColor, 1, 2), 16),
			g = tonumber(string.sub(cleanColor, 3, 4), 16),
			b = tonumber(string.sub(cleanColor, 5, 6), 16)
		}
	elseif (#cleanColor == 3) then
		return {
			r = 17 * tonumber(string.sub(cleanColor, 1, 1), 16),
			g = 17 * tonumber(string.sub(cleanColor, 2, 2), 16),
			b = 17 * tonumber(string.sub(cleanColor, 3, 3), 16)
		}
	end
	error("Invalid hexadecimal color " .. cleanColor, 1)
end

local function round(v)
	if (v < 0) then
		return math.ceil(v - 0.5)
	else
		return math.floor(v + 0.5)
	end
end

local function rgbToHex(r, g, b)
	return string.format("%02X%02X%02X", round(r), round(g), round(b))
end

local function rgbToCmyk(r, g, b)
	if (r > 255 or g > 255 or b > 255 or r < 0 or g < 0 or b < 0) then
		error("Color level out of bounds")
	end
	local c = 1 - r / 255
	local m = 1 - g / 255
	local y = 1 - b / 255
	local k = math.min(c, m, y)
	if (k == 1) then
		c = 0
		m = 0
		y = 0
	else
		local d = 1 - k
		c = (c - k) / d
		m = (m - k) / d
		y = (y - k) / d
	end
	return { c = c * 100, m = m * 100, y = y * 100, k = k * 100 }
end

local function rgbToHsl(r, g, b)
	if (r > 255 or g > 255 or b > 255 or r < 0 or g < 0 or b < 0) then
		error("Color level out of bounds")
	end
	local channelMax = math.max(r, g, b)
	local channelMin = math.min(r, g, b)
	local range = channelMax - channelMin
	local h, s
	if (range == 0) then
		h = 0
	elseif (channelMax == r) then
		h = 60 * ((g - b) / range)
		if (h < 0) then
			h = 360 + h
		end
	elseif (channelMax == g) then
		h = 60 * (2 + (b - r) / range)
	else
		h = 60 * (4 + (r - g) / range)
	end
	local L = channelMax + channelMin
	if (L == 0 or L == 510) then
		s = 0
	else
		s = 100 * range / math.min(L, 510 - L)
	end
	return { h = h, s = s, l = L * 50 / 255 }
end

local function rgbToHsv(r, g, b)
	if (r > 255 or g > 255 or b > 255 or r < 0 or g < 0 or b < 0) then
		error("Color level out of bounds")
	end
	local channelMax = math.max(r, g, b)
	local channelMin = math.min(r, g, b)
	local range = channelMax - channelMin
	local h, s
	if (range == 0) then
		h = 0
	elseif (channelMax == r) then
		h = 60 * ((g - b) / range)
		if (h < 0) then
			h = 360 + h
		end
	elseif (channelMax == g) then
		h = 60 * (2 + (b - r) / range)
	else
		h = 60 * (4 + (r - g) / range)
	end
	if (channelMax == 0) then
		s = 0
	else
		s = 100 * range / channelMax
	end
	return { h = h, s = s, v = channelMax * 100 / 255 }
end

-- c in [0, 255], condition tweaked for no discontinuity
-- http://entropymine.com/imageworsener/srgbformula/
local function toLinear(c)
	if (c > 10.314300250662591) then
		return math.pow((c + 14.025) / 269.025, 2.4)
	else
		return c / 3294.6
	end
end

local function toNonLinear(c)
	if (c > 0.00313066844250063) then
		return 269.025 * math.pow(c, 1.0/2.4) - 14.025
	else
		return 3294.6 * c
	end
end

local function srgbToCielchuvD65o2deg(r, g, b)
	if (r > 255 or g > 255 or b > 255 or r < 0 or g < 0 or b < 0) then
		error("Color level out of bounds")
	end
	local R = toLinear(r)
	local G = toLinear(g)
	local B = toLinear(b)
	-- https://github.com/w3c/csswg-drafts/issues/5922
	local X = 0.1804807884018343 * B + 0.357584339383878 * G + 0.41239079926595934 * R
	local Y = 0.07219231536073371 * B + 0.21263900587151027 * R + 0.715168678767756 * G
	local Z = 0.01933081871559182 * R + 0.11919477979462598 * G + 0.9505321522496607 * B
	local L, C, h
	if (Y > 0.00885645167903563082) then
		L = 116 * math.pow(Y, 1/3) - 16
	else
		L = Y * 903.2962962962962962963
	end
	if ((r == g and g == b) or L == 0) then
		C = 0
		h = 0
	else
		d = X + 3 * Z + 15 * Y
		if (d == 0) then
			C = 0
			h = 0
		else
			-- 0.19783... and 0.4631... computed with extra precision from (X,Y,Z) when (R,G,B) = (1,1,1),
			-- in which case (u,v) ≈ (0,0)
			local us = 4 * X / d - 0.19783000664283678994
			local vs = 9 * Y / d - 0.46831999493879099801
			h = math.atan2(vs, us) * 57.2957795130823208768
			if (h < 0) then
				h = h + 360
			elseif (h == 0) then
				h = 0 -- ensure zero is positive
			end
			C = math.sqrt(us * us + vs * vs) * 13 * L
			if (C == 0) then
				C = 0
				h = 0
			end
		end
	end
	return { L = L, C = C, h = h }
end

local function srgbMix(t, r0, g0, b0, r1, g1, b1)
	if (t > 1 or t < 0) then
		error("Interpolation parameter out of bounds")
	end
	if (r0 > 255 or g0 > 255 or b0 > 255 or r1 > 255 or g1 > 255 or b1 > 255 or r0 < 0 or g0 < 0 or b0 < 0 or r1 < 0 or g1 < 0 or b1 < 0) then
		error("Color level out of bounds")
	end
	local tc = 1 - t
	return {
		r = toNonLinear(tc * toLinear(r0) + t * toLinear(r1)),
		g = toNonLinear(tc * toLinear(g0) + t * toLinear(g1)),
		b = toNonLinear(tc * toLinear(b0) + t * toLinear(b1))
	}
end

local function formatToPrecision(value, p)
	return string.format("%." .. p .. "f", value)
end

local function getFractionalZeros(p)
	if (p > 0) then
		return "." .. string.rep("0", p)
	else
		return ""
	end
end

function p.hexToRgbTriplet(frame)
	local args = frame.args or frame:getParent().args
	local hex = args[1]
	if (hex) then
		local rgb = hexToRgb(hex)
		return rgb.r .. ', ' .. rgb.g .. ', ' .. rgb.b
	else
		return ""
	end
end

function p.rgbTripletToHex(frame)
	local args = frame.args or frame:getParent().args
	local r = tonumber(args[1])
	local g = tonumber(args[2])
	local b = tonumber(args [3])
	if (isempty(r) or isempty(g) or isempty(b)) then
		return ""
	else
		return rgbToHex(r,g,b)
	end
end

function p.hexToCmyk(frame)
	local args = frame.args or frame:getParent().args
	local hex = args[1]
	if (hex) then
		local p = tonumber(args.precision) or 0
		local s = args.pctsign or "1"
		local rgb = hexToRgb(hex)
		local cmyk = rgbToCmyk(rgb.r, rgb.g, rgb.b)
		local fk = formatToPrecision(cmyk.k, p)
		local fc, fm, fy
		local fracZeros = getFractionalZeros(p)
		if (fk == 100  .. fracZeros) then
			local fZero = 0 .. fracZeros
			fc = fZero
			fm = fZero
			fy = fZero
		else
			fc = formatToPrecision(cmyk.c, p)
			fm = formatToPrecision(cmyk.m, p)
			fy = formatToPrecision(cmyk.y, p)
		end
		if (s ~= "0") then
			return fc .. "%, " .. fm .. "%, " .. fy .. "%, " .. fk .. "%"
		else
			return fc .. ", " .. fm .. ", " .. fy .. ", " .. fk
		end
	else
		return ""
	end
end

function p.hexToHsl(frame)
	local args = frame.args or frame:getParent().args
	local hex = args[1]
	if (hex) then
		local p = tonumber(args.precision) or 0
		local rgb = hexToRgb(hex)
		local hsl = rgbToHsl(rgb.r, rgb.g, rgb.b)
		local fl = formatToPrecision(hsl.l, p)
		local fs, fh
		local fracZeros = getFractionalZeros(p)
		local fZero = 0 .. fracZeros
		if (fl == fZero or fl == 100 .. fracZeros) then
			fs = fZero
			fh = fZero
		else
			fs = formatToPrecision(hsl.s, p)
			if (fs == fZero) then
				fh = fZero
			else
				fh = formatToPrecision(hsl.h, p)
				if (fh == 360 .. fracZeros) then
					fh = fZero -- handle rounding to 360
				end
			end
		end
		return fh .. "°, " .. fs .. "%, " .. fl .. "%"
	else
		return ""
	end
end

function p.hexToHsv(frame)
	local args = frame.args or frame:getParent().args
	local hex = args[1]
	if (hex) then
		local p = tonumber(args.precision) or 0
		local rgb = hexToRgb(hex)
		local hsv = rgbToHsv(rgb.r, rgb.g, rgb.b)
		local fv = formatToPrecision(hsv.v, p)
		local fs, fh
		local fracZeros = getFractionalZeros(p)
		local fZero = 0 .. fracZeros
		if (fv == fZero) then
			fh = fZero
			fs = fZero
		else
			fs = formatToPrecision(hsv.s, p)
			if (fs == fZero) then
				fh = fZero
			else
				fh = formatToPrecision(hsv.h, p)
				if (fh == 360 .. fracZeros) then
					fh = fZero -- handle rounding to 360
				end
			end
		end
		return fh .. "°, " .. fs .. "%, " .. fv .. "%"
	else
		return ""
	end
end

function p.hexToCielch(frame)
	local args = frame.args or frame:getParent().args
	local hex = args[1]
	if (hex) then
		local p = tonumber(args.precision) or 0
		local rgb = hexToRgb(hex)
		local LCh = srgbToCielchuvD65o2deg(rgb.r, rgb.g, rgb.b)
		local fL = formatToPrecision(LCh.L, p)
		local fC, fh
		local fracZeros = getFractionalZeros(p)
		local fZero = 0 .. fracZeros
		if (fL == fZero or fL == 100 .. fracZeros) then
			fC = fZero
			fh = fZero
		else
			fC = formatToPrecision(LCh.C, p)
			if (fC == fZero) then
				fh = fZero
			else
				fh = formatToPrecision(LCh.h, p)
				if (fh == 360 .. fracZeros) then
					fh = fZero -- handle rounding to 360
				end
			end
		end
		return fL .. ", " .. fC .. ", " .. fh .. "°"
	else
		return ""
	end
end

function p.hexMix(frame)
	local args = frame.args or frame:getParent().args
	local hex0 = args[1]
	local hex1 = args[2]
	if (isempty(hex0) or isempty(hex1)) then
		return ""
	end
	local t = args[3]
	if (isempty(t)) then
		t = 0.5
	else
		t = tonumber(t)
		local min = tonumber(args.min) or 0
		local max = tonumber(args.max) or 100
		if (min >= max) then
			error("Minimum proportion greater than or equal to maximum")
		elseif (t < min) then
			t = 0
		elseif (t > max) then
			t = 1
		else
			t = (t - min) / (max - min)
		end
	end
	local rgb0 = hexToRgb(hex0)
	local rgb1 = hexToRgb(hex1)
	local rgb = srgbMix(t, rgb0.r, rgb0.g, rgb0.b, rgb1.r, rgb1.g, rgb1.b)
	return rgbToHex(rgb.r, rgb.g, rgb.b)
end

return p
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