Camera Preview (USB)

1. Compile the function package

cd ~/yahboom_ws

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colcon build

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source install/setup.bash

2. Start the camera

Start the camera

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ros2 run camera camera_usb

View nodes and topics

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ros2 node list

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ros2 topic list

3. Preview screen

Use rqt to view the screen corresponding to the camera: rqt → Plugins → Visualization → Image View

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rqt

4. Main code

​x
import rclpy
from rclpy.node import Node
from sensor_msgs.msg import Image
from cv_bridge import CvBridge
import cv2
​
class CameraNode(Node):
    def __init__(self):
        super().__init__('camera_usb')
        self.publisher = self.create_publisher(Image, 'image_raw', 10)
        self.bridge = CvBridge()
        
        self.cap = cv2.VideoCapture(0)
        if not self.cap.isOpened():
            self.get_logger().error('Unable to open camera')
            return
        
        self.timer = self.create_timer(0.05, self.timer_callback)
​
    def timer_callback(self):
        ret, frame = self.cap.read()
        if ret:
            image_msg = self.bridge.cv2_to_imgmsg(frame, encoding="bgr8")
            self.publisher.publish(image_msg)
        else:
            self.get_logger().warn('Failed to capture image')
​
def main(args=None):
    rclpy.init(args=args)
    node = CameraNode()
    rclpy.spin(node)
​
    node.cap.release()
    rclpy.shutdown()
​
if __name__ == '__main__':
    main()