private function setShadowColor($color, $alpha, $type)
    {
        if ($color !== null) {
            $this->shadowProperties['color']['value'] = (string) $color;
        }
        if ($alpha !== null) {
            $this->shadowProperties['color']['alpha'] = $this->getTrueAlpha((int) $alpha);
        }
        if ($type !== null) {
            $this->shadowProperties['color']['type'] = (string) $type;
        }

        return $this;
    }