serializers.py 文件源码

def from_msg(cls, msg):
        """Serializes a ROS Image message into a compressed PNG image.

        Args:
            msg: ROS Image or CompressedImage message.

        Returns:
            Compressed PNG image.

        Raises:
            CvBridgeError: On image conversion error.
        """
        if isinstance(msg, CompressedImage):
            # Decompress message.
            msg = cls.from_raw(msg.data)

        # Convert ROS Image to OpenCV image.
        bridge = CvBridge()
        img = bridge.imgmsg_to_cv2(msg)

        # Convert to PNG with highest level of compression to limit bandwidth
        # usage. PNG is used since it is a lossless format, so this can later
        # be retrieved as a ROS image without issue.
        compression = [cv2.IMWRITE_PNG_COMPRESSION, 9]
        png = cv2.imencode(".png", img, compression)[1].tostring()

        return png