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I'm following these tutorials to stream images to OpenCV format from the /ardrone/image_raw topic.

http://wiki.ros.org/cv_bridge/Tutorials/UsingCvBridgeToConvertBetweenROSImagesAndOpenCVImages

However, even though I've been able to successfully compile the driver, when i run it, I don't see any images on screen. My code is this -

#include "ros/ros.h"
#include <image_transport/image_transport.h>
#include <cv_bridge/cv_bridge.h>
#include <sensor_msgs/image_encodings.h>
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/imgproc/imgproc.hpp>
#include "ardrone_autonomy/Navdata.h"

static const std::string OPENCV_WINDOW = "Image window";

class ImageConverter
{
  ros::NodeHandle nh_;
  image_transport::ImageTransport it_;      //ImageTransport object "it_" under the namespace 'image_transport'
  image_transport::Subscriber image_sub_;       //Subscriber object "image_sub_"
  image_transport::Publisher image_pub_;        // Publisher object "image_pub_"
  
   public:
    ImageConverter(): it_(nh_)
    {
        // Subscribe to input video feed and publish output video feed
      image_sub_ = it_.subscribe("/ardrone/image_raw", 1,&ImageConverter::imageCb, this);
      image_pub_ = it_.advertise("/image_converter/output_video", 1);

          cv::namedWindow(OPENCV_WINDOW);
    }

    ~ImageConverter()
    {
            cv::destroyWindow(OPENCV_WINDOW);
    }

   void imageCb(const sensor_msgs::ImageConstPtr& msg)
    {
      cv_bridge::CvImagePtr cv_ptr;
      try
      {
        cv_ptr = cv_bridge::toCvCopy(msg, sensor_msgs::image_encodings::BGR8);
      }
      catch (cv_bridge::Exception& e)
      {
      ROS_ERROR("cv_bridge exception: %s", e.what());
      return;
    }

    // Draw an example circle on the video stream
    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));

    // Update GUI Window
    cv::imshow(OPENCV_WINDOW, cv_ptr->image);
    cv::waitKey(3);
    
    // Output modified video stream
    image_pub_.publish(cv_ptr->toImageMsg());
  }
};

int main(int argc, char** argv)
{
  ros::init(argc, argv, "see_image");
  ImageConverter ic;
  ros::spin();
  return 0;
}

After executing this, rosrun [package_name] [driver_node] along with a recorded .bag file, it is supposed to produce image stream with a circle on it.

I can see when I run rqt_graph both the bag file and the driver node. However, I don't see any image. What am I missing? I've lost about a week in looking at this.


Originally posted by voladoddi on ROS Answers with karma: 87 on 2014-09-26

Post score: 0

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1 Answer 1

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For those who are stuck in the same position as me, you might want to check your bag file. Mine didn't have any images in them.

But I got stuck here for a while because /ardrone/image_raw was displayed when I called rostopic list. In this case you want to make sure that your images were considerable in message numbers.

  1. Check your rosbag using rosbag info [bag_file] to see if the message is listed.
  2. Try visualizing in rviz if the image is displayed while running the bag file.
  3. rqt_graph for connection of topics.

Cheers.


Originally posted by voladoddi with karma: 87 on 2014-09-26

This answer was ACCEPTED on the original site

Post score: 0

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