simple ros node to display camera stream using opencv

cv_image_stream.py

#!/usr/bin/env python
import threading
import rospy
import numpy as np

from sensor_msgs.msg import Image
from cv_bridge import CvBridge, CvBridgeError
import cv2

camera_image=np.zeros((480, 640, 3), np.uint8)
image_lock=threading.Lock()
quit_event=threading.Event()
update_event=threading.Event()

bridge=CvBridge()

def display_func(quit_ev, im_lock, cam_img, update_ev):
        print(id(cam_img))
        local_image=np.zeros((480, 640, 3), np.uint8)
        cv2.namedWindow("image", flags=cv2.WINDOW_AUTOSIZE)
        cv2.moveWindow("image", 0, 0)
        while not quit_ev.is_set():
                if update_ev.is_set():
                        im_lock.acquire()
                        print(id(cam_img))
                        np.copyto(local_image, cam_img)
                        im_lock.release()
                        update_ev.clear()
                cv2.imshow("image", local_image)
                cv2.waitKey(100)

def image_callback(msg, cam_im, im_lock, update_ev):
        try:
                cv_img=bridge.imgmsg_to_cv2(msg, "bgr8")
        except CvBridgeError, e:
                print(e)
        else:
                im_lock.acquire()
                np.copyto(cam_im, cv_img)
                print(id(cam_im))
                im_lock.release()
                update_ev.set()

def main():
        print(id(camera_image))
        display_thread=threading.Thread(target=display_func, args=(quit_event, image_lock, camera_image, update_event))
        callback_partial=lambda x:image_callback(x, camera_image, image_lock, update_event)
        rospy.init_node("image_listener")
        image_topic="/cv_camera/image_raw"
        rospy.Subscriber(image_topic, Image, callback_partial)
        display_thread.start()
        rospy.spin()
        quit_event.set()


if __name__=="__main__":
        main()