ROS开发过程

1.Python环境

----python  pip  
sudo apt install python3-pip
sudo pip3 install --upgrade pip

--python  Opencv
OpenCV3在Python中包名称是cv2，而不是cv3？
	实际上，”cv2”中的”2”并不表示OpenCV的版本号。
	OpenCV是基于C/C++的，”cv”和”cv2”表示的是底层C API和C++API的区别，”cv2”表示使用的是C++API
opencv-contrib-python 与 opencv-python 有何不同
	一个是基本装opencv，带contrib的是高配版，带一些收费或者专利的算
pip3 -V
pip -V
pip3 install opencv-python -i https://mirrors.aliyun.com/pypi/simple/
python
	import cv2
	print(cv2.__version__)

2.C++ opencv环境

在Ubuntu14.04和16.04下一般运行  sudo apt-get install libopencv-dev
Ubuntu18.04中  sudo apt-get install libopencv-dev   
-- 查看版本 pkg-config --modversion opencv

＃必须指定到包含 .cmake的上一层
	set(OpenCV_DIR   /usr/share/OpenCV)　　
	find_package(OpenCV REQUIRED)

3.Ros运行

01.启动 roscore;
	roscore
02.编译Mes
  流程:
	按照固定格式创建 msg 文件
	编辑配置文件
	编译生成可以被 Python 或 C++ 调用的中间文件
    编译后的中间文件查看
      C++ 需要调用的中间文件(.../工作空间/devel/include/包名/xxx.h)
      Python 需要调用的中间文件(.../工作空间/devel/lib/python3/dist-packages/包名/msg)

	cd   ~/code/work_project/src
	catkin_create_pkg vision roscpp std_msgs cv_bridge sensor_msgs
	cd   ~/code/work_project
	catkin_make

03.启动发布节点;
	cd ~/Data
	rosbag play -l Evaluation.bag
 

04.启动订阅节点 
	mkdir vision/scripts
	cd  ~/code/work_project/vision/scripts
	touch HelloImg.py
	chmod +x HelloImg.py
	cd ..
  vim CamkeList.txt


	cd ~/code/work_project
	catkin_make
	source ./devel/setup.bash   
	rosrun vision view_sub
05.启动查看  rviz是ros自带的一个图形化工具，可以方便的对ros的程序进行图形化操作
	cd ~/code/work_project
	rviz

06.杀死ros进程
	killall -9 roscore
	killall -9 rosmaster

4.Ros步骤

##只播放感兴趣的 topic ，则用命令
 rosbag play  ~/Data/Evaluation.bag  --topic  /usb_cam/image_raw
 rosbag play -l Evaluation.bag
 rosbag info ~/Data/Evaluation.bag
 rosbag play  ~/Data/Evaluation.bag  --topic  /usb_cam/image_raw
	空格键可以恢复/暂停播放

rostopic info /usb_cam/image_raw
rostopic type /usb_cam/image_raw
rostopic echo /usb_cam/image_raw
rosmsg show  sensor_msgs/Image   

topic
	/usb_cam/image_raw       msgs    : sensor_msgs/Image      
common_msgs: sensor_msgs 消息的定义和使用
http://docs.ros.org/en/api/sensor_msgs/html/msg/Image.htm
     sensor_msgs/CameraInfo              
         sensor_msgs/CompressedImage         
         sensor_msgs/Image                    
         sensor_msgs/Imu                              

rostopic info /usb_cam/image_raw
Type: sensor_msgs/Image
Publishers: 
	* /play_123 (http://Ubuntu-111:39395/)
Subscribers: None

header: 
  seq: 46699
  stamp: 
    secs: 1626943378
    nsecs: 834539851
  frame_id: "usb_cam"
height: 240
 320
encoding: "rgb8"
is_bigendian: 0
step: 960
data:

5.ROS使用Opencv

ROS以其自己的sensor_msgs/Image消息格式发布图像
CvBridge是一个ROS库，提供ROS和OpenCV之间的接口。 可以在vision_opencvv堆栈的cv_bridge软件包中找到CvBridge
使用CvBridge将ROS图像转换为OpenCV cv::Matt格式
将OpenCV图像转换为ROS格式，以便通过ROS发布图像消息

:~/code/work_project$ locate OpenCVConfig.cmake
	/usr/share/OpenCV/OpenCVConfig.cmake


set(Opencv_DIR /usr/share/OpenCV)
find_package( Opencv  NAMES OpenCV REQUIRED)

6.错误处理

----ModuleNotFoundError: No module named ‘skbuild‘
sudo apt install cmake

pip install scikit-build
法
pip3 uninstall opencv-python

1.image_sub = rospy.Subscriber('camera/rgb/image_raw', Image, imaghe_callback)
ouldn't find executable named ImgVision.py below /home//code/work_project/src/vision
[rosrun] Found the following, but they're either not files,
[rosrun] or not executable:
[rosrun]   /home/traveler/code/work_project/src/vision/scripts/ImgVision.py
traveler@Ubuntu-069:~/code/work_project$ chmod +x /home/traveler/code/work_project/src/vision/scripts/ImgVision.py
   注意c++的代码是不需要加后缀的
    rosrun  vision grayImage
    rosrun  vision ImgVision.py
    2.错误类型
TypeError: unbound method onlyCellValue() must be called with dictionary instance as first argument (got str instance instead)
CvBridge.bridge.imgmsg_to_cv2
后经在网上查看，发现时由于调用其他类时，未在后面添加括号，添加括号后，运行正常 CvBridge().bridge.imgmsg_to_cv2

Ros命名

Valid Names
  A valid name has the following characteristics:
     First character is an alpha character ([a-z|A-Z]), tilde (~) or forward slash (/)
      Subsequent characters can be alphanumeric ([0-9|a-z|A-Z]), underscores (_), or forward slashes (/)
Exception: base names (described below) cannot have forward slashes (/) or tildes (~) in them.

参考：

ROS机器人编程实践----琐碎知识点 https://www.cnblogs.com/dingyc/p/10676756.html