ros2_simple_image_subscriber.py

#!/usr/bin/env python3
import rclpy
from rclpy.node import Node
from sensor_msgs.msg import Image
from cv_bridge import CvBridge
import cv2

class ImageSubscriber(Node):
    def __init__(self):
        super().__init__('image_subscriber')
        self.declare_parameter('camera_topic','/navigation_camera/image_raw')
        self.camera_topic = self.get_parameter('camera_topic').value
        self.subscription = self.create_subscription(
            Image,
            self.camera_topic, 
            self.image_callback,
            1)
        self.cv_bridge = CvBridge()

    def image_callback(self, msg):
        try:
            cv_image = self.cv_bridge.imgmsg_to_cv2(msg, "bgr8")
        except Exception as e:
            self.get_logger().error("Error converting ROS Image to OpenCV image: %s" % str(e))
            return
        cv2.imshow("Image", cv_image)
        cv2.waitKey(1)

def main(args=None):
    rclpy.init(args=args)
    image_subscriber = ImageSubscriber()
    rclpy.spin(image_subscriber)
    image_subscriber.destroy_node()
    rclpy.shutdown()

if __name__ == '__main__':
    main()

To be used for testing the below PR
hello-robot/stretch_ros2#105