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realtime image subscriber

asked 2019-10-02 03:35:46 -0500

mingcheng gravatar image

updated 2019-10-02 05:02:33 -0500

Hi, I wrote a subscriber to subscribe the image message send from the topic /gi/simulation/left/image_raw and convert it using CV.bridge(). However, the problem is that, this subscriber only shows a single frame of image when the subscriber starts. Is there a way that my subscriber can achieve the similar effect when I using rviz to subscribe to the same topic. In simple, how to achieve real time image capture by using the subscriber. The code for subscriber is shown below: Thank you for the help.

#!/usr/bin/env python
import rospy
import sys
import cv2
from cv_bridge import CvBridge
from sensor_msgs.msg import Image

def process_image(msg):
    bridge = CvBridge()
    img = bridge.imgmsg_to_cv2(msg, "bgr8")
    cv2.imshow("image",img)
    cv2.waitKey(0)
if __name__ == '__main__':
    while not rospy.is_shutdown():
        rospy.init_node('image_sub')
        rospy.loginfo('image_sub node started')
        rospy.Subscriber("/gi/simulation/left/image_raw", Image, process_image)

        rospy.spin()
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answered 2019-10-02 05:05:15 -0500

The problem is caused by cv2.waitKey(0) in you image callback. If you pass zero to waitKey it will pause until you press a key with the window focused, and block execution of your program.

If you change this :

cv2.waitKey(50)

This instead it will wait for 50 milliseconds or until you press a key and then continue execution, allowing your code to receive and display more images.

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Comments

Thank you very much for helping, the problem is solved. :D

mingcheng gravatar imagemingcheng ( 2019-10-03 02:17:18 -0500 )edit

Great. Can you accept the answer by clicking on the tick icon. That way other users can easily see that your question has a solution.

PeteBlackerThe3rd gravatar imagePeteBlackerThe3rd ( 2019-10-03 03:58:12 -0500 )edit

ok, done thank you~

mingcheng gravatar imagemingcheng ( 2019-10-03 04:16:01 -0500 )edit

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Asked: 2019-10-02 03:35:46 -0500

Seen: 18 times

Last updated: Oct 02