How to properly convert hsl colors to rgb colors in lua?

Question

I have the following code:

#!/usr/bin/env lua5.3
-- Code adapted from https://github.com/EmmanuelOga/columns/blob/master/utils/color.lua#L51

local function hslToRgb(h, s, l, a)
    local r, g, b

    h = (h / 255)
    s = (s / 100)
    l = (l / 100)

    if s == 0 then
        r, g, b = l, l, l -- achromatic
    else
        local function hue2rgb(p, q, t)
            if t < 0   then t = t + 1 end
            if t > 1   then t = t - 1 end
            if t < 1/6 then return p + (q - p) * 6 * t end
            if t < 1/2 then return q end
            if t < 2/3 then return p + (q - p) * (2/3 - t) * 6 end
            return p
        end

        local q
        if l < 0.5 then q = l * (1 + s) else q = l + s - l * s end
        local p = 2 * l - q

        r = hue2rgb(p, q, h + 1/3)
        g = hue2rgb(p, q, h)
        b = hue2rgb(p, q, h - 1/3)
    end

    if not a then a = 1 end
    return r * 255, g * 255, b * 255, a * 255
end

local h,s,l,a
h,s,l,a = hslToRgb(220, 16.4, 21.6)

print(h,s,l,a)
-- expected output: 46  52  64  255
--   actual output: 64.11312    46.04688    60.92496    255

But, as stated at the end, the color values it outputs are completely wrong. The decimals are not an issue (as in, it's not an issue that it outputs them; their values are still wrong).

Answer 1

A hue value it's calculated in degrees, so the max isn't 255, but 360:

function hslToRgb(h, s, l)
    h = h / 360
    s = s / 100
    l = l / 100

    local r, g, b;

    if s == 0 then
        r, g, b = l, l, l; -- achromatic
    else
        local function hue2rgb(p, q, t)
            if t < 0 then t = t + 1 end
            if t > 1 then t = t - 1 end
            if t < 1 / 6 then return p + (q - p) * 6 * t end
            if t < 1 / 2 then return q end
            if t < 2 / 3 then return p + (q - p) * (2 / 3 - t) * 6 end
            return p;
        end

        local q = l < 0.5 and l * (1 + s) or l + s - l * s;
        local p = 2 * l - q;
        r = hue2rgb(p, q, h + 1 / 3);
        g = hue2rgb(p, q, h);
        b = hue2rgb(p, q, h - 1 / 3);
    end

    if not a then a = 1 end
    return r * 255, g * 255, b * 255, a * 255
end

You can see this code working here.