使用Python进行ros图像的发送

使用Python进行ros图像的发送

这里首先要完成ros和Pycharm联合编程的设置，具体可以参考qt和pycharm联合ros编程的设置
之后如果用到处理图像的这块的话，就需要下面cv_bridge的使用。

一、首先进行cv_bridge的编译

因为原来系统自带的cv_bridge只能在python2下使用，所以这里需要python3编译一下cv_bridge。

1、首先进入系统真正的空间中：打开一个新的终端，最好运行一下

source deactivate

2、首先进入python3的环境并安装相关依赖包

sudo apt-get install python-catkin-tools python3-dev python3-catkin-pkg-modules python3-numpy python3-yaml ros-kinetic-cv-bridge

3、创建一个工作空间用于存放待编译的 cv_bridge 文件

mkdir -p catkin_workspace/src

4、指示catkin设置cmake变量

cd catkin_workspace

catkin config -DPYTHON_EXECUTABLE=/usr/bin/python3 -DPYTHON_INCLUDE_DIR=/usr/include/python3.5m -DPYTHON_LIBRARY=/usr/lib/x86_64-linux-gnu/libpython3.5m.so

5、Instruct catkin to install built packages into install place。这一步不成功也没关系，可不用

catkin config --install

6、在catkin_workspace工作空间中克隆 cv_bridge src

git clone https://github.com/ros-perception/vision_opencv.git src/vision_opencv

7、Find version of cv_bridge in your repository

apt-cache show ros-kinetic-cv-bridge | grep Version

8、Checkout right version in git repo. In our case it is 1.12.8

cd src/vision_opencv/
git checkout 1.12.8
cd ../../

9、这里可能会有一个问题提前说一下，如果编译过程中遇到下面的问题。（提前看一下下面这个东西，如果是不对的，提前改过来）

CMake Error at /usr/share/cmake-3.6/Modules/FindBoost.cmake:1677 (message):
  Unable to find the requested Boost libraries.

  Boost version: 1.58.0

  Boost include path: /usr/include

  Could not find the following Boost libraries:

          boost_python3

  No Boost libraries were found.  You may need to set BOOST_LIBRARYDIR to the
  directory containing Boost libraries or BOOST_ROOT to the location of
  Boost.
Call Stack (most recent call first):
  CMakeLists.txt:11 (find_package)

这是因为CMake试图找到libboost_python3.so库，但是在ubuntu中它是libboost_python-py35.so（/usr/lib/x86_64-linux-gnu/libboost_python-py35.so）。因此应该在文件src/vision_opencv/cv_bridge/CMakeLists.txt中将下面这行更改find_package()中的内容，更改为python-py35。然后再重新编译：

原始行：

find_package(Boost REQUIRED python3)

更改成：

find_package(Boost REQUIRED python-py35)

10、最后进行编译

catkin build

11、验证：在install的同级目录下打开终端，在终端下面进行Python的验证，如果没有问题的话证明成功了

source install/setup.bash --extend
python3
from cv_bridge.boost.cv_bridge_boost import getCvType

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至此，使用python3编译好的cv_bridge已经存在于路径

二、图像发布、订阅的脚本编写

1、首先查看默认的cv_bridge的位置在哪里（’/opt/ros/kinetic/lib/python2.7/dist-packages/cv_bridge/init.py’）

python3
import cv_bridge
cv_bridge.__file__
# 这样就可以看到cv_bridge的默认路径了

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2、下面再看看我们上面用python3编译好的cv_bridge的路径**(一定要在编译好的工作空间下打开，这里的编译的工作空间在/home/wl/software/ros_cvbridge/)**

source install/setup.bash --extend
python3
import cv_bridge
cv_bridge.__file__

可以看到我们我们编译好的cv_bridge的路径是（’/home/wl/software/ros_cvbridge/install/lib/python3/dist-packages/cv_bridge/init.py’）

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下面找到了路径以后要就可以进行talker.py和listener.py就可以了

三、Pycharm编译ROS发布图像的发布订阅的节点消息。

1、首先下面的这个程序是摄像头捕捉图像，并且发出去的程序。看程序的注释，里面有几个需要注意的点，还是值得关注一下。

talk.py

#!/usr/bin/env python
# license removed for brevity
import os
envpath = '/home/wl/anaconda3/envs/image_location/lib/python3.6/site-packages/cv2/qt/plugins/platforms'
os.environ['QT_QPA_PLATFORM_PLUGIN_PATH'] = envpath
import rospy
import sys

# 下面这个sensor_msg.msg一定要写在path.remove之前，否则把路径一旦remove的话，再import这样是会报错的

from sensor_msgs.msg import Image
sys.path.remove('/opt/ros/kinetic/lib/python2.7/dist-packages')
import cv2
sys.path.append('/home/wl/software/ros_cvbridge/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 os
envpath = '/home/wl/anaconda3/envs/image_location/lib/python3.6/site-packages/cv2/qt/plugins/platforms'
os.environ['QT_QPA_PLATFORM_PLUGIN_PATH'] = envpath
import rospy
import sys
from sensor_msgs.msg import Image
sys.path.remove('/opt/ros/kinetic/lib/python2.7/dist-packages')
import cv2
sys.path.append('/home/wl/software/ros_cvbridge/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()