public function toAttr($prefix='', $suffix='') {
        $attrs = array();
        if ($this->width !== FALSE) {
            $attrs[] = 'width="'.addslashes($this->width).'"';
        }
        if ($this->height !== FALSE) {
            $attrs[] = 'height="'.addslashes($this->height).'"';
        }
        return $prefix.implode(' ', $attrs).$suffix;
    }