color library

color = {}
color.__index = color
function color:new(r, g, b, a)
    self = setmetatable({}, self)

    if type(r) == 'string' then
        self:fromHex(r)
    else
        self:setRGB(r, g, b, a)
    end

    return self
end

function color:white()
    for i = 1, 4 do self[i] = 1 end
    return self
end

function color:black()
    for i = 1, 3 do self[i] = 0 end
    self[4] = 1
    return self
end

function color:setRGB(r, g, b, a)
    self[1] = r and r/255 or self[1] or 0
    self[2] = g and g/255 or self[2] or 0
    self[3] = b and b/255 or self[3] or 0
    self[4] = a and a/255 or self[4] or 1
end

function color:getRGB()
    return unpack(self)
end

function color:fromHex(hex)
    self:black()
    hex = hex:gsub('%X', '') -- remove non-hex chars

    local l = #hex

    -- Short with/without alpha (FFF/FFFF)
    -- Long with/without alpha (FFFFFF/FFFFFFFF)
    assert( l == 3 or l == 4 or l == 6 or l == 8, 'Invalid hex format')

    local mul = l > 4 and 1/255 or 16/255

    local i = 0
    for c in hex:gmatch(l > 4 and '%x%x' or '%x') do
            i = i + 1
            self[i] = tonumber(c, 16) * mul
    end

    return self
end

function color:fromHSV(h, s, v, a)
    local r, g, b
    local i = math.floor(h * 6);
    local f = h * 6 - i;
    local p = v * (1 - s);
    local q = v * (1 - f * s);
    local t = v * (1 - (1 - f) * s);

    i = i % 6
    if i == 0 then
        r, g, b = v, t, p
    elseif i == 1 then
        r, g, b = q, v, p
    elseif i == 2 then
        r, g, b = p, v, t
    elseif i == 3 then
        r, g, b = p, q, v
    elseif i == 4 then
        r, g, b = t, p, v
    elseif i == 5 then
        r, g, b = v, p, q
    end
    self[1], self[2], self[3] = r, g, b
    self[4] = a or self[4] or 1
    return self
end

function color:toHSV()
    local r, g, b, a = self[1], self[2], self[3], self[4]

    local max, min = math.max(r, g, b), math.min(r, g, b)
    local h, s, v
    v = max

    local d = max - min
    if max == 0 then s = 0 else s = d / max end

    if max == min then
        h = 0 -- achromatic
    else
        if max == r then
            h = (g - b) / d
            if g < b then h = h + 6 end
        elseif max == g then
            h = (b - r) / d + 2
        elseif max == b then
            h = (r - g) / d + 4
        end
        h = h / 6
    end

    return h, s, v, a
end


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

function color:fromHSL(h, s, l, a)
    local r, g, b

    if s == 0 then
        r, g, b = l, l, l -- achromatic
    else
        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

    self[1] = r
    self[2] = g
    self[3] = b
    self[4] = a and a or self[4]
end

function color:toHSL()
    local r, g, b

    if s == 0 then
        r, g, b = l, l, l -- achromatic
    else
        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

    self[1] = r
    self[2] = g
    self[3] = b
    self[4] = a and a or self[4]
end

function color:setHue(value)
    local h, s, v, a = self:toHSV(); h = value
    self:fromHSV(h, s, v, a)
end

function color:setSat(value)
    local h, s, v, a = self:toHSV(); s = value
    self:fromHSV(h, s, v, a)
end

function color:setVal(value)
    local h, s, v, a = self:toHSV(); v = value
    self:fromHSV(h, s, v, a)
end

return color