ROS images和OpenCV images之间的转化

操作环境

　　OS：Ubuntu 12.04

　　ROS Version：groovy

操作步骤

1：利用catkin新建一个workspace叫ros_opencv,并进行初始化

1 $ mkdir -p ros_opencv/src
2 $ cd ros_opencv/src
3 $ catkin_init_workspace

2：进入src目录，新建一个package叫opencv_test

1 $ catkin_create_pkg opencv_test sensor_msgs opencv2 cv_bridge roscpp std_msgs image_transport

3：修改opencv_test目录下CMakeLists.txt文件，代码如下

 1 cmake_minimum_required(VERSION 2.8.3)
 2 project(opencv_test)
 3 
 4 ## Find catkin macros and libraries
 5 
 6 find_package(catkin  REQUIRED COMPONENTS cv_bridge image_transport  roscpp sensor_msgs std_msgs)
 7 find_package(OpenCV REQUIRED)
 8 
 9 ## Declare a catkin package
10 catkin_package()
11 
12 ## Include directories,
13 ## Add target and link libraries
14 
15 include_directories(include ${OpenCV_INCLUDE_DIRS})
16 include_directories(include ${catkin_INCLUDE_DIRS})
17 
18 add_executable(opencv_test_node src/opencv_test_node.cpp)
19 target_link_libraries(opencv_test_node ${catkin_LIBRARIES} ${OpenCV_LIBRARIES})
20 add_dependencies(opencv_test_node opencv_test_gencpp)

4:在src下添加源代码

 1 #include <ros/ros.h>
 2 #include <stdio.h>
 3 #include <image_transport/image_transport.h>
 4 #include <cv_bridge/cv_bridge.h>
 5 #include <sensor_msgs/image_encodings.h>
 6 #include <opencv2/imgproc/imgproc.hpp>
 7 #include <opencv2/highgui/highgui.hpp>
 8 
 9 static const char WINDOW[] = "Image window";
10 static void help()
11 {
12     printf("\nThis program demonstrates converting OpenCV Image to ROS Image messages  \n"
13         );
14 
15 }
16 
17 int main(int argc, char** argv)
18 {
19   help();
20   ros::init(argc, argv, "image_converter");
21 
22   //Reading an image from the file
23   cv::Mat cv_image = cv::imread(image directory);
24   if(cv_image.empty() )
25     {
26         ROS_ERROR("Read the picture failed!");
27         return -1;
28     }
29 
30   //Convert OpenCV image to ROS message
31   ros::NodeHandle node;
32   image_transport::ImageTransport transport(node);
33   image_transport::Publisher image_pub; 
34   image_pub=transport.advertise("OutImage", 1);
35   ros::Time time=ros::Time::now(); 
36 
37   cv_bridge::CvImage cvi;
38   cvi.header.stamp = time;
39   cvi.header.frame_id = "image";
40   cvi.encoding = "bgr8";
41   cvi.image = cv_image;
42 
43   sensor_msgs::Image im;
44   cvi.toImageMsg(im);
45   image_pub.publish(im);
46   ROS_INFO("Converted Successfully!");
47 
48   //Show the image
49   cv::namedWindow(WINDOW);
50   cv::imshow(WINDOW,cv_image);
51   cv::waitKey(0);
52 
53   ros::spin();
54   return 0;
55 }

5：在ros_opencv目录下进行 catkin_make

1 $ catkin_make

6：运行

1 $ roscore
2 #open a new terminal
3 $ source devel/setup.bash
4 $ rosrun opencv_test opencv_test_node

注意的地方

因为最新推出的ros版本中默认使用的是catkin（一种类似与cmake的工程构建工具，不过仍然兼容原来的构建方式rosbuild），因此在参考相关的学习资料时要特别注意两者的区别，比如说像指令和CMakeLists.txt中的代码等;
运行时，在输入rosrun之前，要先 source devel/setup.bash，不然会出现无法找到package之类的错误;

参考资料

Converting between ROS images and OpenCV images (C++)》
《ROS tutorial》
How to make ROS and Opencv work together》

Steven Meng

2013.5.12