protected function imageThumb($width, $height)
    {
        $width = (int) $width;
        $height = (int) $height;
        if ($width <= 0) {
            throw new BadMethodCallException('Invalid parameter width for command "thumb"');
        }
        if ($height <= 0) {
            throw new BadMethodCallException('Invalid parameter height for command "thumb"');
        }
        $this->image = $this->image->thumbnail(new Box($width, $height));
    }