Revision history [back]

There are probably a fair number of ROS users who are learning C++, so the following links may be useful.

For why things are done this way: https://isocpp.org/wiki/faq/pointers-to-members

For the standard library way to solve the problem (note the differences between C++98 and C++11): http://www.cplusplus.com/reference/functional/bind/?kw=bind .

There are probably a fair number of ROS users who are learning C++, so the following links may be useful.

For why things are done this way: https://isocpp.org/wiki/faq/pointers-to-members

For the standard library way to solve the problem (note the differences between C++98 and C++11): http://www.cplusplus.com/reference/functional/bind/?kw=bind .

This code works, using boost::bind , though others may suggest better ways:

#include <string>  
#include <iomanip> 
#include <sstream> 
#include <fstream>
#include <functional>

// image subscriber
#include <ros/ros.h>
#include <image_transport/image_transport.h>
#include <opencv2/highgui/highgui.hpp>
#include <cv_bridge/cv_bridge.h>
#include <camera_info_manager/camera_info_manager.h>
#include <boost/assign/list_of.hpp>

// opencv2.4
#include <opencv2/core/core.hpp>
#include <opencv2/video/tracking.hpp>
#include <opencv2/imgproc/imgproc.hpp> 

using namespace cv;
using namespace std;
typedef const boost::function< void(const sensor_msgs::ImageConstPtr &)>  callback;

class myImages {
  public:
    cv::Mat myMatImage1;
    sensor_msgs::ImagePtr myMessagePtr;
    void imageCallback(const sensor_msgs::ImageConstPtr& msg );
};

static void wrapper_imageCallback(void* pt2Object, const sensor_msgs::ImageConstPtr& msg);

void myImages::imageCallback(const sensor_msgs::ImageConstPtr& msg )
{
  try
  {
    this->myMatImage1 = cv_bridge::toCvShare(msg, "bgr8")->image;
    cv::imshow("view", this->myMatImage1);
    cv::waitKey(30);
    this->myMessagePtr = cv_bridge::CvImage(std_msgs::Header(), "bgr8", this->myMatImage1).toImageMsg();  
  }
  catch (cv_bridge::Exception& e)
  {
    ROS_ERROR("Could not convert from '%s' to 'bgr8'.", msg->encoding.c_str());
  }
}

static void wrapper_imageCallback(void* pt2Object, const sensor_msgs::ImageConstPtr& msg)
   {
       myImages* mySelf = (myImages*) pt2Object; // explicitly cast to a pointer to class myImages
       mySelf->imageCallback(msg );          // call member
   }

int main(int argc, char **argv)
{
  ros::init(argc, argv, "flow_vision");
  ros::NodeHandle nh;
  cv::namedWindow("view");
  cv::startWindowThread();
  image_transport::ImageTransport it(nh);
  myImages MyImagesObj;
  callback boundImageCallback = boost::bind(&myImages::imageCallback, &MyImagesObj/*&images*/, _1); 
  // "_1" is a place holder for the first (and only) parameter of myImages::imageCallback(const sensor_msgs::ImageConstPtr& msg )
  /*subscribe (
   * const std::string &base_topic,
   * uint32_t queue_size,
   * const boost::function< void(const sensor_msgs::ImageConstPtr &)>       &callback,
   * const ros::VoidPtr &tracked_object=ros::VoidPtr(),
   * const TransportHints &transport_hints=TransportHints()) 
   */
  image_transport::Subscriber sub = it.subscribe("camera/image_raw", 1, boundImageCallback);
  image_transport::Publisher pub = it.advertise("out_flow_vision_image_base_topic", 1);
  ros::Rate loop_rate(15);  //need to increase for video
  while (nh.ok()) {
    pub.publish(MyImagesObj.myMessagePtr);
    ros::spinOnce();
    loop_rate.sleep();
  }
  cv::destroyWindow("view");
}