import rclpy from rclpy.node import Node from sensor_msgs.msg import Image from cv_bridge import CvBridge import cv2 import numpy as np
class ImageSubscriber(Node): """ Create an ImageSubscriber class, which is a subclass of the Node class. """ def __init__(self): """ Class constructor to set up the node """ # Initiate the Node class's constructor and give it a name super().__init__('image_subscriber') # Create the subscriber. This subscriber will receive an Image # from the video_frames topic. The queue size is 10 messages. self.subscription = self.create_subscription( Image, 'video_frames', self.listener_callback, 10) self.subscription # prevent unused variable warning # Used to convert between ROS and OpenCV images self.br = CvBridge() def listener_callback(self, data): """ Callback function. """ # Display the message on the console self.get_logger().info('Receiving video frame') # Convert ROS Image message to OpenCV image current_frame = self.br.imgmsg_to_cv2(data) # Display image cv2.imshow("camera", current_frame) cv2.waitKey(1) def main(args=None): # Initialize the rclpy library rclpy.init(args=args) # Create the node image_subscriber = ImageSubscriber() # Spin the node so the callback function is called. rclpy.spin(image_subscriber) # Destroy the node explicitly # (optional - otherwise it will be done automatically # when the garbage collector destroys the node object) image_subscriber.destroy_node() # Shutdown the ROS client library for Python rclpy.shutdown() if __name__ == '__main__': main()
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