最近来公司实习，开始接触ROS（机器人操作系统），以下为工作笔记，如有不足请各位大牛们指出

作用描述：

（1）建立两个节点image_node_a 和  image_node_b;

（2）节点image_node_a在一个topic——node_a下发布图像message;

（3）节点image_node_b订阅topic——node_a；

（4）然后节点image_node_b又把收到的信息转换为opencv格式的图像进行处理；

（5）接着节点image_node_b把处理后的信息又在topic——node_b下发布出去；

（6）最后，node_a订阅topic——node_b。

一、节点node_a

在工作空间～/catkin_ws/src下新建一个文件夹——image_node_a，该文件夹下包含一个src的文件夹、一个CMakeLists.txt、一个package.xml，具体内容如下所示：

1  src/image_node_a.cpp文件

#include <ros/ros.h> #include <image_transport/image_transport.h> #include <opencv2/highgui/highgui.hpp> #include <cv_bridge/cv_bridge.h> void imageCallback(const sensor_msgs::ImageConstPtr& tem_msg) { try { cv::imshow("node_a listener from node_b", cv_bridge::toCvShare(tem_msg, "mono8")->image); cv::waitKey(30); } catch (cv_bridge::Exception& e) { ROS_ERROR("Could not convert from '%s' to 'mono8'.", tem_msg->encoding.c_str()); } } int main(int argc, char** argv) { ros::init(argc, argv, "image_node_a"); ros::NodeHandle nh; image_transport::ImageTransport it(nh); image_transport::Publisher pub = it.advertise("node_a", 1); image_transport::Subscriber sub = it.subscribe("node_b",1,imageCallback); //cv::Mat image = cv::imread(argv[1], CV_LOAD_IMAGE_COLOR); cv::Mat image = cv::imread("/home/ding/lena.jpeg", CV_LOAD_IMAGE_COLOR); cv::waitKey(30); sensor_msgs::ImagePtr msg = cv_bridge::CvImage(std_msgs::Header(), "bgr8", image).toImageMsg(); ros::Rate loop_rate(5); while (nh.ok()) { pub.publish(msg); ros::spinOnce(); loop_rate.sleep(); } }

2  CMakeLists.txt

cmake_minimum_required(VERSION 2.8.3) project(image_node_a) set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11") if(WIN32 AND NOT CYGWIN) set(HOME $ENV{PROFILE}) else() set(HOME $ENV{HOME}) endif() find_package(catkin REQUIRED COMPONENTS roscpp rospy std_msgs sensor_msgs cv_bridge image_transport ) find_package(OpenCV REQUIRED) catkin_package(CATKIN_DEPENDS roscpp std_msgs sensor_msgs ) include_directories( include ${OpenCV_INCLUDE_DIRS} ${catkin_INCLUDE_DIRS} ) ### find files file(GLOB_RECURSE HEADER_FILES ${CMAKE_CURRENT_SOURCE_DIR}/include/*.h*) file(GLOB_RECURSE SOURCE_FILES ${CMAKE_CURRENT_SOURCE_DIR}/src/*.c*) add_executable(image_node_a ${HEADER_FILES} ${SOURCE_FILES} ) target_link_libraries(image_node_a ${catkin_LIBRARIES} ${OpenCV_LIBRARIES} )

3  package.xml

<?xml version="1.0"?> <package>   <name>image_node_a</name>   <version>0.0.0</version>   <description>The image_node_a package</description>   <maintainer email="abc@ding.com">abc</maintainer>   <license>TODO</license>    <build_depend>message_generation</build_depend>    <run_depend>message_runtime</run_depend>    <build_depend>opencv2</build_depend>    <run_depend>opencv2</run_depend>   <buildtool_depend>catkin</buildtool_depend>       <build_depend>roscpp</build_depend>   <build_depend>sensor_msgs</build_depend>   <build_depend>std_msgs</build_depend>   <build_depend>cv_bridge</build_depend>   <build_depend>image_transport</build_depend>     <run_depend>roscpp</run_depend>   <run_depend>sensor_msgs</run_depend>   <run_depend>std_msgs</run_depend>   <run_depend>cv_bridge</run_depend>   <run_depend>image_transport</run_depend>   <export>   </export> </package>

二、节点node_b

在工作空间～/catkin_ws/src下新建一个文件夹——image_node_b，该文件夹下包含一个src的文件夹、一个CMakeLists.txt、一个package.xml，具体内容如下所示：

1  image_node_b.cpp

#include "ros/ros.h" #include "image_transport/image_transport.h" #include "cv_bridge/cv_bridge.h" #include "sensor_msgs/image_encodings.h" #include <opencv2/imgproc/imgproc.hpp> #include <opencv2/highgui/highgui.hpp> #include <iostream> namespace enc = sensor_msgs::image_encodings; /*准备再次发布的图像显示到本窗口*/ //static const char OUT_WINDOW[] = "Image Out"; /*读取订阅的图像并显示到本窗口*/ //static std::string IN_WINDOW = "Image In"; class ImageConvertor { ros::NodeHandle nh_; image_transport::ImageTransport it_; image_transport::Subscriber image_sub_; image_transport::Publisher image_pub_; public: ImageConvertor():it_(nh_){ /*发布主题out*/ image_pub_ = it_.advertise("node_b", 1); /*订阅主题camera/image*/ image_sub_ = it_.subscribe("node_a", 1, &ImageConvertor::ImageCb, this); //cv::namedWindow(OUT_WINDOW, CV_WINDOW_AUTOSIZE); //cv::namedWindow(IN_WINDOW, CV_WINDOW_AUTOSIZE); } ~ImageConvertor() { //cv::destroyWindow(IN_WINDOW); //cv::destroyWindow(OUT_WINDOW); } void ImageCb(const sensor_msgs::ImageConstPtr& msg) { cv_bridge::CvImagePtr cv_ptr; try { /*转化成CVImage*/ cv_ptr = cv_bridge::toCvCopy(msg, enc::BGR8); cv::imshow("node_b listener from node_a",cv_ptr->image); cv::waitKey(30); } catch (cv_bridge::Exception& e) { ROS_ERROR("cv_bridge exception is %s", e.what()); return; } if(cv_ptr->image.rows > 60 && cv_ptr->image.cols > 60) cv::circle(cv_ptr->image, cv::Point(50,50), 10, CV_RGB(255,0,0)); //cv::imshow(IN_WINDOW, cv_ptr->image); cv::Mat img_out; /*convert RGB to GRAY*/ cv::cvtColor(cv_ptr->image, img_out, CV_RGB2GRAY); //cv::imshow(OUT_WINDOW, img_out); cv::imshow("node_b talker to node_c",img_out); cv::waitKey(3); /*转化成ROS图像msg发布到主题out*/ image_pub_.publish(cv_ptr->toImageMsg()); } }; int main(int argc, char** argv) { ros::init(argc, argv, "image_node_b"); ImageConvertor ic; ros::spin(); return 0; }

2  CMakeLists.txt

cmake_minimum_required(VERSION 2.8.3) project(image_node_b) set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11") if(WIN32 AND NOT CYGWIN) set(HOME $ENV{PROFILE}) else() set(HOME $ENV{HOME}) endif() find_package(catkin REQUIRED COMPONENTS roscpp rospy std_msgs sensor_msgs cv_bridge image_transport ) find_package(OpenCV REQUIRED) catkin_package(CATKIN_DEPENDS roscpp std_msgs ) include_directories( include ${OpenCV_INCLUDE_DIRS} ${catkin_INCLUDE_DIRS} ) ### find files file(GLOB_RECURSE HEADER_FILES ${CMAKE_CURRENT_SOURCE_DIR}/include/*.h*) file(GLOB_RECURSE SOURCE_FILES ${CMAKE_CURRENT_SOURCE_DIR}/src/*.c*) add_executable(image_node_b ${HEADER_FILES} ${SOURCE_FILES} ) target_link_libraries(image_node_b ${catkin_LIBRARIES} ${OpenCV_LIBRARIES} )

3  package.xml

<?xml version="1.0"?> <package> <name>image_node_b</name> <version>0.0.0</version> <description>The image_node_b package</description> <maintainer email="abc@ding.com">abc</maintainer> <license>TODO</license> <build_depend>message_generation</build_depend> <run_depend>message_runtime</run_depend> <build_depend>opencv2</build_depend> <run_depend>opencv2</run_depend> <buildtool_depend>catkin</buildtool_depend> <build_depend>roscpp</build_depend> <build_depend>sensor_msgs</build_depend> <build_depend>std_msgs</build_depend> <build_depend>cv_bridge</build_depend> <build_depend>image_transport</build_depend> <run_depend>roscpp</run_depend> <run_depend>sensor_msgs</run_depend> <run_depend>std_msgs</run_depend> <run_depend>cv_bridge</run_depend> <run_depend>image_transport</run_depend> <export> </export> </package>

三、编译节点

分别按照如下步骤在终端上运行：

export ROS_PACKAGE_PATH=~/catkin_ws/src:$ROS_PACKAGE_PATH roscd image_node_a cd ../.. catkin_make

四、运行节点

1   打开一个新的终端

roscore

2 再打开一个新的终端

cd ~/catkin_ws source ./devel/setup.bash rosrun image_node_a  image_node_a

3  再打开一个新的终端

cd ~/catkin_ws source ./devel/setup.bash rosrun image_node_b  image_node_b 到此终于大功告成了， 你可以看到如下的结果：

参考文献：

1 http://blog.csdn.net/github_30605157/article/details/50990493 2  http://blog.csdn.net/x_r_su/article/details/52704193 3 http://wiki.ros.org/image_transport/Tutorials 4 http://wiki.ros.org/ROS/Tutorials/WritingPublisherSubscriber(c++)