public function generateThumbnail($id, $width, $height = null)
	{
		if ($height === null)
		{
			$height = $width;
		}

		$temp = $this->container->download($id);

		$img = new \Imagick($temp->getPath());
		$img->cropThumbnailImage($width, $height);
		$img->writeImage();

		return $this->container->upload($temp);
	}