From ba221060c5f61456177c4a7f7cb408cf190391cf Mon Sep 17 00:00:00 2001
From: Max Cahill <1bardesign@gmail.com>
Date: Mon, 15 Jun 2020 21:11:05 +1000
Subject: [PATCH] [modified] colour fairly extensively; renamed functions to
 same snake_case convention as other modules [added] colour.hsl_to_rgb

---
 colour.lua | 98 ++++++++++++++++++++++++++++++++++++++++++------------
 1 file changed, 76 insertions(+), 22 deletions(-)

diff --git a/colour.lua b/colour.lua
index eb5868e..5774719 100644
--- a/colour.lua
+++ b/colour.lua
@@ -1,23 +1,40 @@
 --[[
 	colour handling stuff
-
-	feel free to alias to `color` :)
 ]]
 
+local path = (...):gsub("colour", "")
+
 local bit = require("bit")
 local band, bor = bit.band, bit.bor
 local lshift, rshift = bit.lshift, bit.rshift
 
+local math = require(path.."mathx")
+
 local colour = {}
 
-function colour.packRGB(r, g, b)
+-------------------------------------------------------------------------------
+-- hex handling routines
+-- pack and unpack into 24 or 32 bit hex numbers
+
+--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)
 	local bb = lshift(band(0xff, b * 255), 0)
 	return bor( br, bg, bb )
 end
 
-function colour.packARGB(r, g, b, a)
+function colour.unpack_rgb(rgb)
+	local r = rshift(band(rgb, 0x00ff0000), 16) / 255.0
+	local g = rshift(band(rgb, 0x0000ff00), 8)  / 255.0
+	local b = rshift(band(rgb, 0x000000ff), 0)  / 255.0
+	return r, g, b
+end
+
+--argb format (common for shared hex)
+
+function colour.pack_argb(r, g, b, a)
 	local ba = lshift(band(0xff, a * 255), 24)
 	local br = lshift(band(0xff, r * 255), 16)
 	local bg = lshift(band(0xff, g * 255), 8)
@@ -25,15 +42,7 @@ function colour.packARGB(r, g, b, a)
 	return bor( br, bg, bb, ba )
 end
 
-function colour.packRGBA(r, g, b, a)
-	local br = lshift(band(0xff, r * 255), 24)
-	local bg = lshift(band(0xff, g * 255), 16)
-	local bb = lshift(band(0xff, b * 255), 8)
-	local ba = lshift(band(0xff, a * 255), 0)
-	return bor( br, bg, bb, ba )
-end
-
-function colour.unpackARGB(argb)
+function colour.unpack_argb(argb)
 	local r = rshift(band(argb, 0x00ff0000), 16) / 255.0
 	local g = rshift(band(argb, 0x0000ff00), 8)  / 255.0
 	local b = rshift(band(argb, 0x000000ff), 0)  / 255.0
@@ -41,7 +50,17 @@ function colour.unpackARGB(argb)
 	return r, g, b, a
 end
 
-function colour.unpackRGBA(rgba)
+--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)
+	local bb = lshift(band(0xff, b * 255), 8)
+	local ba = lshift(band(0xff, a * 255), 0)
+	return bor( br, bg, bb, ba )
+end
+
+function colour.unpack_rgba(rgba)
 	local r = rshift(band(rgba, 0xff000000), 24) / 255.0
 	local g = rshift(band(rgba, 0x00ff0000), 16) / 255.0
 	local b = rshift(band(rgba, 0x0000ff00), 8)  / 255.0
@@ -49,14 +68,49 @@ function colour.unpackRGBA(rgba)
 	return r, g, b, a
 end
 
-function colour.unpackRGB(rgb)
-	local r = rshift(band(rgb, 0x00ff0000), 16) / 255.0
-	local g = rshift(band(rgb, 0x0000ff00), 8)  / 255.0
-	local b = rshift(band(rgb, 0x000000ff), 0)  / 255.0
-	local a = 1.0
-	return r, g, b, a
+-------------------------------------------------------------------------------
+-- colour space conversion
+-- rgb is the common language 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
+function colour.hsl_to_rgb(h, s, l)
+	--wedge slice
+	local w = (math.wrap(h, 0, 1) * 6)
+	--chroma
+	local c = (1 - math.abs(2 * l - 1)) * s
+	--secondary
+	local x = c * (1 - math.abs(w % 2 - 1))
+	--lightness boost
+	local m = l - c / 2
+	--per-wedge logic
+	local r, g, b = m, m, m
+	if w < 1 then
+		r = r + c
+		g = g + x
+	elseif w < 2 then
+		r = r + x
+		g = g + c
+	elseif w < 3 then
+		g = g + c
+		b = b + x
+	elseif w < 4 then
+		g = g + x
+		b = b + c
+	elseif w < 5 then
+		b = b + c
+		r = r + x
+	else
+		b = b + x
+		r = r + c
+	end
+	return r, g, b
 end
 
---todo: hsl, hsv, other colour spaces
+--todo: rgb to hsl
 
-return colour
\ No newline at end of file
+--todo: hsv, other colour spaces
+
+
+return colour