private function init() {
        if ($this->im === null) {
            $this->im = imagecreatetruecolor($this->w, $this->h)
            or die('Can\'t Initialize the GD Libraty');
            imagefilledrectangle($this->im, 0, 0, $this->w - 1, $this->h - 1, $this->color->allocate($this->im));
        }
    }