crosshairs_nodelet.cpp

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#include <string>

#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/imgproc/imgproc.hpp>

#include <ros/ros.h>
#include <nodelet/nodelet.h>
#include <image_transport/image_transport.h>
#include <sensor_msgs/image_encodings.h>
#include <sensor_msgs/Image.h>
#include <cv_bridge/cv_bridge.h>

namespace swri_image_util
{
  class CrosshairsNodelet : public nodelet::Nodelet
  {
  public:
    CrosshairsNodelet()
    {
    }

    ~CrosshairsNodelet()
    {
    }

    void onInit()
    {
      ros::NodeHandle &node = getNodeHandle();
      ros::NodeHandle &priv = getPrivateNodeHandle();

      image_transport::ImageTransport it(node);
      image_pub_ = it.advertise("crosshairs_image", 1);
      image_sub_ = it.subscribe("image", 1, &CrosshairsNodelet::ImageCallback, this);
    }

    void ImageCallback(const sensor_msgs::ImageConstPtr& image)
    {
      cv_bridge::CvImagePtr cv_image = cv_bridge::toCvCopy(image);
      // Get image dimensions
      const int h = cv_image->image.rows;
      const int w = cv_image->image.cols;
      // Define line properties
      const cv::Scalar black(0, 0, 0);
      const int thickness = 3;
      const int line_type = 8;  // 8-connected line
      // Draw vertical line
      cv::line(cv_image->image, cv::Point(0, w/2), cv::Point(h-1, w/2), black, thickness, line_type);
      // Draw horizontal line
      cv::line(cv_image->image, cv::Point(h/2, 0), cv::Point(h/2, w-1), black, thickness, line_type);
      // Publish image
      image_pub_.publish(cv_image->toImageMsg());
    }

  private:
    image_transport::Subscriber image_sub_;
    image_transport::Publisher image_pub_;
  };
}

// Register nodelet plugin
#include <swri_nodelet/class_list_macros.h>
SWRI_NODELET_EXPORT_CLASS(swri_image_util, CrosshairsNodelet);