ROSCPP + OpenCV Program

Basically, here I am demonstrating how you can start writing your own program with ROS.

Create ROS package. Follow the tutorial link here. I am assuming that ros_workspace folder is added into ROS_PACKAGE_PATH

$ cd ~/ros_workspace

$ roscreate-pkg tbsimctrl std_msgs roscpp opencv2 sensor_msgs cv_bridge image_transport

You may not all the dependencies mentioned above.

$ cd tbsimctrl

$ rospack profile

$ rospack find tbsimctrl

/home/turtlebot/ros_workspace/tbsimctrl

Now create a file “camera_test.cpp” under src folder. The file contains the following piece of code:

#include

#include    //may not be needed

#include  //may not be needed

#include  //may not be needed

#include

#include

#include

#include

using namespace std;

using namespace cv;

int main(int argc, char **argv)

{

  ros::init(argc, argv, "captureimg");

  ros::NodeHandle n;

  CvCapture* capture = cvCaptureFromCAM(-1);

  cvSetCaptureProperty(capture, CV_CAP_PROP_FRAME_WIDTH, 320);

  cvSetCaptureProperty(capture, CV_CAP_PROP_FRAME_HEIGHT, 240);

  IplImage *img = 0;

  img = cvQueryFrame(capture);

  int frameH = (int) cvGetCaptureProperty(capture, CV_CAP_PROP_FRAME_HEIGHT);

  int frameW = (int) cvGetCaptureProperty(capture, CV_CAP_PROP_FRAME_WIDTH);

  int fps = (int) cvGetCaptureProperty(capture, CV_CAP_PROP_FPS);

  cout << frameW << “\t” << frameH << “\t” << fps << endl;

  cvNamedWindow("Left", CV_WINDOW_AUTOSIZE);

  for(int n = 1; n= 30; n++)

  {

        img = cvQueryFrame(capture);

        cvShowImage("Left", img);  //show frames while capturing

        int c = cvWaitKey(20);               // wait 20 ms

        if(c == 27)

          break;

  }

  cvDestroyWindow( "Left" );

  cvReleaseCapture(&capture);

  return 0;

}

The above program captures video from a webcam. Save the file and insert the following statement inside the CMakeLists.txt file inside the tbsimctrl package folder. 

rosbuild_add_executable(${PROJECT_NAME} src/camera_test.cpp)

Now compile and build the package using rosmake

$ cmake .

$ rosmake

Make sure that the package is built with 0 failures. Once it is done, you can test the code as follows:

$ rosrun tbsimctrl tbsimctrl

You should be able to see the video from your webcam.