Color3 Lerping Function

ModuleScripts/LerpColor3.lua

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+-- Combines two colors in CIELUV space.
+-- Color3 LerpCIELUV(Color3 fromColor, Color3 toColor, float t)
+-- @author Fraktality
+
+-- https://www.w3.org/Graphics/Color/srgb
+
+local Black = Color3.fromRGB(0, 0, 0)
+
+return function(c0, c1, t)
+	local u0, v0, u1, v1
+
+	-- Convert from linear RGB to scaled CIELUV (RgbToLuv13)
+	local r, g, b = c0.r, c0.g, c0.b
+	-- Apply inverse gamma correction
+	r = r < 0.0404482362771076 and r/12.92 or 0.87941546140213*(r + 0.055)^2.4
+	g = g < 0.0404482362771076 and g/12.92 or 0.87941546140213*(g + 0.055)^2.4
+	b = b < 0.0404482362771076 and b/12.92 or 0.87941546140213*(b + 0.055)^2.4
+	-- sRGB->XYZ->CIELUV
+	local y = 0.2125862307855956*r + 0.71517030370341085*g + 0.0722004986433362*b
+	local z = 3.6590806972265883*r + 11.4426895800574232*g + 4.1149915024264843*b
+	local l0 = y > 0.008856451679035631 and 116*y^(1/3) - 16 or 903.296296296296*y
+	if z > 1e-15 then
+		u0, v0 = l0*(0.9257063972951867*r - 0.8333736323779866*g - 0.09209820666085898*b)/z, l0*(9*y/z - 0.46832)
+	else
+		u0, v0 = -0.19783*l0, -0.46832*l0
+	end
+
+	-- Convert from linear RGB to scaled CIELUV (RgbToLuv13)
+	r, g, b = c1.r, c1.g, c1.b
+	-- Apply inverse gamma correction
+	r = r < 0.0404482362771076 and r/12.92 or 0.87941546140213*(r + 0.055)^2.4
+	g = g < 0.0404482362771076 and g/12.92 or 0.87941546140213*(g + 0.055)^2.4
+	b = b < 0.0404482362771076 and b/12.92 or 0.87941546140213*(b + 0.055)^2.4
+	-- sRGB->XYZ->CIELUV
+	y = 0.2125862307855956*r + 0.71517030370341085*g + 0.0722004986433362*b
+	z = 3.6590806972265883*r + 11.4426895800574232*g + 4.1149915024264843*b
+	local l1 = y > 0.008856451679035631 and 116*y^(1/3) - 16 or 903.296296296296*y
+	if z > 1e-15 then
+		u1, v1 = l1*(0.9257063972951867*r - 0.8333736323779866*g - 0.09209820666085898*b)/z, l1*(9*y/z - 0.46832)
+	else
+		u1, v1 = -0.19783*l1, -0.46832*l1
+	end
+
+	-- The inputs aren't needed anymore, so don't drag out their lifetimes
+	-- c0, c1 = nil, nil
+
+	-- return function(t)
+	-- Interpolate
+	local l = (1 - t)*l0 + t*l1
+	if l < 0.0197955 then
+		return Black
+	end
+	local u = ((1 - t)*u0 + t*u1)/l + 0.19783
+	local v = ((1 - t)*v0 + t*v1)/l + 0.46832
+
+	-- CIELUV->XYZ
+	y = (l + 16)/116
+	y = y > 0.206896551724137931 and y*y*y or 0.12841854934601665*y - 0.01771290335807126
+	local x = y*u/v
+	z = y*((3 - 0.75*u)/v - 5)
+
+	-- XYZ->linear sRGB
+	r =  7.2914074*x - 1.5372080*y - 0.4986286*z
+	g = -2.1800940*x + 1.8757561*y + 0.0415175*z
+	b =  0.1253477*x - 0.2040211*y + 1.0569959*z
+
+	-- Adjust for the lowest out-of-bounds component
+	if r < 0 and r < g and r < b then
+		r, g, b = 0, g - r, b - r
+	elseif g < 0 and g < b then
+		r, g, b = r - g, 0, b - g
+	elseif b < 0 then
+		r, g, b = r - b, g - b, 0
+	end
+
+	-- Apply gamma correction
+	r = r < 3.1306684425e-3 and 12.92*r or 1.055*r^(1/2.4) - 0.055
+	g = g < 3.1306684425e-3 and 12.92*g or 1.055*g^(1/2.4) - 0.055
+	b = b < 3.1306684425e-3 and 12.92*b or 1.055*b^(1/2.4) - 0.055
+
+	return Color3.new(
+		-- Clamp the result
+		r > 1 and 1 or r < 0 and 0 or r,
+		g > 1 and 1 or g < 0 and 0 or g,
+		b > 1 and 1 or b < 0 and 0 or b
+	)
+	-- end
+end