Merge branch 'feature/nobit-colour'

colour.lua

@@ -14,28 +14,12 @@ local colour = {}
 -- pack and unpack into 24 or 32 bit hex numbers
 
 local ok, bit = pcall(require, "bit")
-if not ok then
-	for _, v in ipairs{
-		"pack_rgb",
-		"unpack_rgb",
-		"pack_argb",
-		"unpack_argb",
-		"pack_rgba",
-		"unpack_rgba",
-	} do
-		colour[v] = function()
-			error(
-				"batteries.colour requires the bit operations module for pack/unpack functionality.\n"
-				.."\tsee https://bitop.luajit.org/\n\n"
-				.."error from require(\"bit\"):\n\n"..bit)
-		end
-	end
-else
+if ok then
+	--we have bit operations module, use the fast path
 	local band, bor = bit.band, bit.bor
 	local lshift, rshift = bit.lshift, bit.rshift
 
 	--rgb only (no alpha)
-
 	function colour.pack_rgb(r, g, b)
 		local br = lshift(band(0xff, r * 255), 16)
 		local bg = lshift(band(0xff, g * 255), 8)
@@ -69,7 +53,6 @@ else
 	end
 
 	--rgba format
-
 	function colour.pack_rgba(r, g, b, a)
 		local br = lshift(band(0xff, r * 255), 24)
 		local bg = lshift(band(0xff, g * 255), 16)
@@ -85,13 +68,55 @@ else
 		local a = rshift(band(rgba, 0x000000ff), 0)  / 255
 		return r, g, b, a
 	end
+else
+	--we don't have bitops, use a slower pure-float path
+	local floor = math.floor
+
+	--rgb only (no alpha)
+	function colour.pack_rgb(r, g, b)
+		local br = floor(0xff * r) % 0x100 * 0x10000
+		local bg = floor(0xff * g) % 0x100 * 0x100
+		local bb = floor(0xff * b) % 0x100
+		return br + bg + bb
+	end
+
+	function colour.unpack_rgb(rgb)
+		local r = floor(rgb / 0x10000) % 0x100
+		local g = floor(rgb / 0x100) % 0x100
+		local b = floor(rgb) % 0x100
+		return r / 255, g / 255, b / 255
+	end
+
+	--argb format (common for shared hex)
+	function colour.pack_argb(r, g, b, a)
+		local ba = floor(0xff * a) % 0x100 * 0x1000000
+		return colour.pack_rgb(r, g, b) + ba
+	end
+
+	function colour.unpack_argb(argb)
+		local r, g, b = colour.unpack_rgb(argb)
+		local a = floor(argb / 0x1000000) % 0x100
+		return r, g, b, a / 255
+	end
+
+	--rgba format
+	function colour.pack_rgba(r, g, b, a)
+		local ba = floor(0xff * a) % 0x100
+		return colour.pack_rgb(r, g, b) * 0x100 + ba
+	end
+
+	function colour.unpack_rgba(rgba)
+		local r, g, b = colour.unpack_rgb(floor(rgba / 0x100))
+		local a = floor(rgba) % 0x100
+		return r, g, b, a
+	end
 end
 
 
 -------------------------------------------------------------------------------
 -- colour space conversion
--- rgb is the common language but it's useful to have other spaces to work in
--- for us as humans :)
+-- rgb is the common language for computers
+-- but it's useful to have other spaces to work in for us as humans :)
 
 --convert hsl to rgb
 --all components are 0-1, hue is fraction of a turn rather than degrees or radians
@@ -145,11 +170,10 @@ function colour.rgb_to_hsl(r, g, b)
 	else
 		h = (r - g) / d + 4
 	end
-	assert(h)
 	return h / 6, s, l
 end
 
---todo: hsv, other colour spaces
+--todo: hsv
 
 --oklab https://bottosson.github.io/posts/oklab/
 function colour.oklab_to_rgb(l, a, b)