-- すべて[0,1]の範囲に正規化してください
-- Hue(色相) [0,1] / Saturation(彩度) [0,1] / Value(明度) [0,1]
function HSVtoRGB(h, s, v)
    local r = v
    local g = v
    local b = v

    if 0 < s then
        h = h * 6.0
        local i = math.floor(h)
        local f = h - i

        if i == 0 then
            g = 1.0 - s * (1.0 - f)
            b = 1.0 - s
        end
        if i == 1 then
            r = 1.0 - s * f
            b = 1.0 - s
        end
        if i == 2 then
            r = 1.0 - s
            b = 1.0 - s * (1.0 - f)
        end
        if i == 3 then
            r = 1.0 - s
            g = 1.0 - s * f
        end
        if i == 4 then
            r = 1.0 - s * (1.0 - f)
            g = 1.0 - s
        end
        if i == 5 then
            g = 1.0 - s
            b = 1.0 - s * f
        end
    end
    return Color.__new(r, g, b)
end