python stream image convert image to meta

Here is a node that listens to a ROS image message topic, converts the images into an cv::Mat, draws a circle on it and displays the image using OpenCV. In this way, future consumers will know whether the image they receive is RGB or BGR. However, the special commonly used image formats above (bgr8, rgb8, etc.) will insert information into the image message about the channel ordering. The ROS image message must always have the same number of channels and pixel depth as the cv::Mat. However, cv2_to_imgmsg() does not do any conversions for you (use CvtColor and ConvertScale instead).

It does, as before, refer to the cv::Mat. The use of 'encoding' is slightly more complicated in this case. cv2_to_imgmsg( cv_image, encoding= ' passthrough ') To convert an cv::Mat into a ROS image message, CvBridge provides the following function:ġ from cv_bridge import CvBridge 2 bridge = CvBridge() 3 image_message = bridge. Note that mono8 and bgr8 are the two image encodings expected by most OpenCV functions.Ĭonverting OpenCV images to ROS image messages Rgba8: CV_8UC4, RGB color image with an alpha channel Rgb8: CV_8UC3, color image with red-green-blue color orderīgra8: CV_8UC4, BGR color image with an alpha channel To use this feature, specify the encoding to be one of the following strings:īgr8: CV_8UC3, color image with blue-green-red color order Image encodings can be any one of the following OpenCV image encodings:įor popular image encodings, CvBridge will optionally do color or pixel depth conversions as necessary. If the default value of 'passthrough' is given, the destination image encoding will be the same as the image message encoding. The encoding refers to the destination cv::Mat image. The input is the image message, as well as an optional encoding. imgmsg_to_cv2( image_message, desired_encoding= ' passthrough ') To convert a ROS image message into an cv::Mat, module cv_bridge.CvBridge provides the following function:ġ from cv_bridge import CvBridge 2 bridge = CvBridge() 3 cv_image = bridge. You will also learn how to convert OpenCV images to ROS format to be published over ROS.Ĭonverting ROS image messages to OpenCV images In this tutorial, you will learn how to write a node that uses CvBridge to convert ROS images into OpenCV cv::Mat format. CvBridge can be found in the cv_bridge package in the vision_opencv stack. CvBridge is a ROS library that provides an interface between ROS and OpenCV.

ROS passes around images in its own sensor_msgs/Image message format, but many users will want to use images in conjunction with OpenCV. Next Tutorial: Converting between ROS images and OpenCV images (Android Java) Keywords: image, images, OpenCV, cvbridge, CvBridge Included is a sample node that can be used as a template for your own node. Don't forget to include in your question the link to this page, the versions of your OS & ROS, and also add appropriate tags.Ĭonverting between ROS images and OpenCV images (Python) Description: This tutorial describes how to interface ROS and OpenCV by converting ROS images into OpenCV images, and vice versa, using cv_bridge. Please ask about problems and questions regarding this tutorial on.

Python stream image convert image to meta