改写图像发布、订阅脚本

上个博客介绍了如何解决cv_bridge与python3的兼容问题，但在执行 talker.py 脚本的时候还是会报错误，那么原因是什么呢？

1. 首先我们来查看默认的 cv_bridge 的位置在哪里

可以看到，他还是去默认存放cv_bridge的文件路径里面去找了
具体存放文件路径是 /opt/ros/melodic/lib/python2.7/dist-packages
那么我们编译好的文件存放到哪里了？

2. 查找编译好的cv_bridge

我们来找找，我们先切换到我们的工作空间
执行

source install/setup.bash --extend

然后进入python3，查找编译好的cv_bridge位置

python3
import cv_bridge
cv_bridge.__file__

如下图所示

可以看到，我们编译好的cv_bridge存放的路径是
/home/zhm/openSource/catkin_workspace/install/lib/python3/dist-packages

3.修改talker.py 和 listener.py

好了，现在我们找到了存放路径，来改 talker.py 和 listener.py 的代码，很简单，只需要3行代码。
具体的代码如下所示。

• talker.py

#!/usr/bin/env python
# license removed for brevity
import rospy
from sensor_msgs.msg import Image
import cv2
import sys
sys.path.remove('/opt/ros/melodic/lib/python2.7/dist-packages')
sys.path.append('/home/zhm/openSource/catkin_workspace/install/lib/python3/dist-packages')
from cv_bridge import CvBridge

def talker():
     pub = rospy.Publisher('/tutorial/image', Image, queue_size=1) 
     rospy.init_node('talker', anonymous=True) 
     rate = rospy.Rate(30)
     bridge = CvBridge()
     Video = cv2.VideoCapture(0)
     while not rospy.is_shutdown():
         ret, img = Video.read()
         cv2.imshow("talker", img)
         cv2.waitKey(3)
         pub.publish(bridge.cv2_to_imgmsg(img, "bgr8"))
         rate.sleep()

if __name__ == '__main__':
     try:
         talker()
     except rospy.ROSInterruptException:
         pass

• listener.py

#!/usr/bin/python
import rospy
from sensor_msgs.msg import Image
import cv2
import sys
sys.path.remove('/opt/ros/melodic/lib/python2.7/dist-packages')
sys.path.append('/home/zhm/openSource/catkin_workspace/install/lib/python3/dist-packages')
from cv_bridge import CvBridge

def callback(imgmsg):
    bridge = CvBridge()
    img = bridge.imgmsg_to_cv2(imgmsg, "bgr8")
    cv2.imshow("listener", img)
    cv2.waitKey(3)

def listener():

    # In ROS, nodes are uniquely named. If two nodes with the same
    # node are launched, the previous one is kicked off. The
    # anonymous=True flag means that rospy will choose a unique
    # name for our 'listener' node so that multiple listeners can
    # run simultaneously.
    rospy.init_node('listener', anonymous=True)
    rospy.Subscriber("/tutorial/image", Image, callback)
    # spin() simply keeps python from exiting until this node is stopped
    rospy.spin()
if __name__ == '__main__':
    listener()

4. 验证

• 启动 roscore
• 执行 talker.py，可以看到如下显示

python3 talker.py

• 执行 listener.py

python3 listener.py

至此，我们的图像发布、订阅就写好了，写这个博客主要是因为网上的内容很杂乱，没有一篇具体的写 jetson nano 用 python 编写图像发布、订阅的博客，大家有问题评论区多多交流，欢迎大家赏脸～～

原文链接:https://blog.csdn.net/ABC__xiaoming/article/details/110248335