ROS cv_bridge C ++字符串中的ImagePtr转换

Question

Below code snippet from ros subscriber node where video image frame is subscribed based on topic and displayed. As per my requirement cv_ptr->image needs to be converted in to c++ string so that I can create byte array(vector ) out of that .

void imageCb(const sensor_msgs::ImageConstPtr& msg)
{
    cv_bridge::CvImagePtr cv_ptr;
    try
    {
      cv_ptr = cv_bridge::toCvCopy(msg, enc::BGR8);
    }
    catch (cv_bridge::Exception& e)
    {
      ROS_ERROR("cv_bridge exception: %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(WINDOW, cv_ptr->image);
    cv::waitKey(3);
}

basically I am looking for API which converts cv_ptr->image frame buffer in c++ string .After subscribing image based on topic , I need to convert the same in byte array so that it can be inserted in activemqcpp producer as other end activemqjava subscriber is expecting the same in bytestream format.

string img_string = (copy operation) cv_ptr->image;// Not sure how to copy this buffer in c++ string

vector <unsigned char> vec(img_string.begin().img_string.end());

below is the class specification as per cv_bridge.h file.

class CvImage;
 typedef boost::shared_ptr<CvImage> CvImagePtr;
 typedef boost::shared_ptr<CvImage const> CvImageConstPtr;

 class CvImage
 {
 public:
 std_msgs::Header header; 
 std::string encoding;    
 cv::Mat image;           
 sensor_msgs::ImagePtr toImageMsg() const;

   void toImageMsg(sensor_msgs::Image& ros_image) const;

   typedef boost::shared_ptr<CvImage> Ptr;
   typedef boost::shared_ptr<CvImage const> ConstPtr;

};

Can anybody suggest how to achieve the same in roscpp?

Answer 1

As specified here http://docs.opencv.org/3.1.0/d3/d63/classcv_1_1Mat.html#a4d33bed1c850265370d2af0ff02e1564 OpenCV's Mat class already stores image data as unsigned char array.

The type of cv_ptr->image is already cv::Mat .

All you need to do access its contents like cv_ptr->image.data