//Call Back function for camera subsciber 
void imageCallback(const sensor_msgs::ImageConstPtr& msg){
cv_ptr = cv_bridge::toCvCopy(msg, sensor_msgs::image_encodings::BGR8);
  //cv::imshow("view", cv_ptr->image);
  //cv::waitKey(1);
  cv::cvtColor(cv_ptr->image, image_gray, CV_BGR2GRAY);
  demo.processImage(cv_ptr->image, image_gray);
}