diff --git a/colors.lua b/colors.lua
index 9405bc3..363a40c 100644
--- a/colors.lua
+++ b/colors.lua
@@ -15,6 +15,10 @@ local colors = {}
 --------------------------------------------------------------------------------
 -- Conversion
 
+colors.rgb255_to_rgb1 = function (color)
+    return { color[1]/255, color[2]/255, color[3]/255, (color[4] or 255)/255 }
+end
+
 colors.rgb_to_hsl = function (color)
 	-- Error check
 	assert(type(color) == 'table' and type(color[1]) == 'number' and type(color[2]) == 'number' and type(color[3]) == 'number')
@@ -25,10 +29,9 @@ colors.rgb_to_hsl = function (color)
 	local b = (color[3] == 255 and 1 or color[3]/256)
 
 	local max, min = math.max(r, g, b), math.min(r, g, b)
+	if min == max then  return { 0, 0, (max+min)/2 }  end
+
 	local h, s, l = (max+min)/2, (max+min)/2, (max+min)/2
-	if min == max then
-		return {0, 0, l}
-	end
 
 	local d = max - min
 	s = l > 0.5 and d / (2 - max - min) or d / (max + min)
@@ -82,14 +85,33 @@ colors.hsl_to_rgb = function (color)
 	return { r, g, b }
 end
 
+colors.hsl_to_rgb1 = function (...)
+    return colors.rgb255_to_rgb1(colors.hsl_to_rgb(...))
+end
+
 --------------------------------------------------------------------------------
 -- Interpolation
 
 colors.interpolate_rgb = function (c1, c2, t)
-	return { c1[1]+(c2[1]-c1[1])*t, c1[2]+(c2[2]-c1[2])*t, c1[3]+(c2[3]-c1[3])*t }
+	assert(type(c1) == 'table' and type(c1[1]) == 'number' and type(c1[2]) == 'number' and type(c1[3]) == 'number' and (type(c1[4]) == 'number' or c1[4] == nil))
+	assert(type(c2) == 'table' and type(c2[1]) == 'number' and type(c2[2]) == 'number' and type(c2[3]) == 'number' and (type(c2[4]) == 'number' or c2[4] == nil))
+	assert(type(t) == 'number')
+	--
+	local alpha = nil
+	if c1[4] or c2[4] then  alpha = (c1[4] or 255) + ((c2[4] or 255)-(c1[4] or 255))*t  end
+	return { c1[1]+(c2[1]-c1[1])*t, c1[2]+(c2[2]-c1[2])*t, c1[3]+(c2[3]-c1[3])*t, alpha }
 end
 
-colors.interpolate_rgb_gamma_adjusted = function (c1, c2, t)
+colors.interpolate_rgb_gamma_adjusted = function (c1, c2, t, gamma)
+    local gamma_inv = nil
+    if not gamma then
+        gamma, gamma_inv = GAMMA, GAMMA_INV
+    else
+        assert(type(gamma) == 'number' and gamma == gamma and gamma ~= 0)
+        gamma_inv = 1 / gamma
+    end
+
+    ----
     local c1_r, c1_g, c1_b = c1[1]^GAMMA, c1[2]^GAMMA, c1[3]^GAMMA
     local c2_r, c2_g, c2_b = c2[1]^GAMMA, c2[2]^GAMMA, c2[3]^GAMMA
     local c3_r, c3_g, c3_b = c1_r+(c2_r-c1_r)*t, c1_g+(c2_g-c1_g)*t, c1_b+(c2_b-c1_b)*t
diff --git a/init.lua b/init.lua
index 86fc208..4a6216b 100644
--- a/init.lua
+++ b/init.lua
@@ -1 +1,2 @@
-return require 'colors.colors'
+
+return require ((...) .. '.colors')