protected function generateBasename()
    {
        $filename = md5($this->image . $this->height . $this->width);

        if (isset(static::$config['default_extension'])) {

            $extension = static::$config['default_extension'];

        } else {

            $extension = pathinfo($this->image, PATHINFO_EXTENSION);

        }

        return $filename . '.' . $extension;   
    }