[Breaking] color: Convert hue [0,359] -> [0,1]

imgui [uses 0-1 for everything internally](
https://github.com/ocornut/imgui/blob/master/imgui.cpp#L2045).

[Both Unity](https://docs.unity3d.com/ScriptReference/Color.RGBToHSV.html)
[and Godot](https://docs.godotengine.org/en/stable/classes/class_color.html#class-color-property-h)
use H, S, and V in the range 0.0 to 1.0

Since we're switching colours out of 0,255 we should also switch hue out
of 0,359. Now all of our r,g,b,a,h,s,v values are all in 0,1.

modules/color.lua

@@ -30,7 +30,7 @@ local function hsv_to_color(hsv)
 		return new(v, v, v, a)
 	end
 
-	h = hsv[1] / 60 -- sector 0 to 5
+	h = hsv[1] * 6 -- sector 0 to 5
 
 	i = math.floor(h)
 	f = h - i -- factorial part of h
@@ -89,10 +89,10 @@ local function color_to_hsv(c)
 		h = 4 + ( r - g ) / delta -- magenta/cyan
 	end
 
-	h = h * 60 -- degrees
+	h = h / 6 -- normalize from segment 0..5
 
 	if h < 0 then
-		h = h + 360
+		h = h + 1
 	end
 
 	return { h, s, v, a }
@@ -132,17 +132,17 @@ function color.new(r, g, b, a)
 end
 
 --- Convert hue,saturation,value table to color object.
--- @tparam table hsva {hue 0-359, saturation 0-1, value 0-1, alpha 0-1}
+-- @tparam table hsva {hue 0-1, saturation 0-1, value 0-1, alpha 0-1}
 -- @treturn color out
 color.hsv_to_color_table = hsv_to_color
 
 --- Convert color to hue,saturation,value table
 -- @tparam color in
--- @treturn table hsva {hue 0-359, saturation 0-1, value 0-1, alpha 0-1}
+-- @treturn table hsva {hue 0-1, saturation 0-1, value 0-1, alpha 0-1}
 color.color_to_hsv_table = color_to_hsv
 
 --- Convert hue,saturation,value to color object.
--- @tparam number h hue 0-359
+-- @tparam number h hue 0-1
 -- @tparam number s saturation 0-1
 -- @tparam number v value 0-1
 -- @treturn color out
@@ -151,7 +151,7 @@ function color.from_hsv(h, s, v)
 end
 
 --- Convert hue,saturation,value to color object.
--- @tparam number h hue 0-359
+-- @tparam number h hue 0-1
 -- @tparam number s saturation 0-1
 -- @tparam number v value 0-1
 -- @tparam number a alpha 0-1
@@ -266,11 +266,11 @@ end
 
 --- Set a color's hue (saturation, value, alpha unchanged)
 -- @tparam color to alter
--- @tparam hue to set 0-359
+-- @tparam hue to set 0-1
 -- @treturn color out
 function color.hue(col, hue)
 	local c = color_to_hsv(col)
-	c[1] = (hue + 360) % 360
+	c[1] = (hue + 1) % 1
 	return hsv_to_color(c)
 end
 

spec/color_spec.lua

@@ -55,7 +55,7 @@ describe("color:", function()
 
 	it("hsv -> rgb -> hsv", function()
 		local hsv1 = { 0, 0.3, 0.8, 0.9 }
-		for h=0,359, 10 do
+		for h=0,1, 0.1 do
 			hsv1[1] = h
 			local cc = color.hsv_to_color_table(hsv1)
 			local hsv2 = cc:color_to_hsv_table()
@@ -83,10 +83,10 @@ describe("color:", function()
 		-- hsv value conversion values from http://colorizer.org/
 		local c = color(122/255, 20/255, 122/255, 1)
 		local hsv = c:color_to_hsv_table()
-		assert_is_approx_equal(hsv[1], 300)
+		assert_is_approx_equal(hsv[1], 300/360)
 		assert_is_approx_equal(hsv[2], 0.8361)
 		assert_is_approx_equal(hsv[3], 0.4784)
-		local r = c:hue(200)
+		local r = c:hue(200/360)
 		assert_is_approx_equal(r[1], 20/255)
 		assert_is_approx_equal(r[2], 88/255)
 		assert_is_approx_equal(r[3], 122/255)