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// https://github.com/Itseez/opencv/blob/2.4/samples/cpp/fback.cpp
/*
 * This program demonstrates dense optical flow algorithm by Gunnar Farneback
 * Mainly the function: calcOpticalFlowFarneback()
 */

#include <ros/ros.h>
#include "opencv_apps/nodelet.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 <opencv2/video/tracking.hpp>

#include <dynamic_reconfigure/server.h>
#include "opencv_apps/FBackFlowConfig.h"
#include "opencv_apps/FlowArrayStamped.h"

namespace fback_flow {
class FBackFlowNodelet : public opencv_apps::Nodelet
{
  image_transport::Publisher img_pub_;
  image_transport::Subscriber img_sub_;
  image_transport::CameraSubscriber cam_sub_;
  ros::Publisher msg_pub_;

  boost::shared_ptr<image_transport::ImageTransport> it_;

  typedef fback_flow::FBackFlowConfig Config;
  typedef dynamic_reconfigure::Server<Config> ReconfigureServer;
  Config config_;
  boost::shared_ptr<ReconfigureServer> reconfigure_server_;

  bool debug_view_;
  ros::Time prev_stamp_;

  std::string window_name_;
  static bool need_config_update_;

  cv::Mat prevgray, gray, flow, cflow;

  void reconfigureCallback(Config &new_config, uint32_t level)
  {
    config_ = new_config;
  }

  const std::string &frameWithDefault(const std::string &frame, const std::string &image_frame)
  {
    if (frame.empty())
      return image_frame;
    return frame;
  }

  void imageCallbackWithInfo(const sensor_msgs::ImageConstPtr& msg, const sensor_msgs::CameraInfoConstPtr& cam_info)
  {
    do_work(msg, cam_info->header.frame_id);
  }

  void imageCallback(const sensor_msgs::ImageConstPtr& msg)
  {
    do_work(msg, msg->header.frame_id);
  }

  static void trackbarCallback( int, void* )
  {
    need_config_update_ = true;
  }

  void do_work(const sensor_msgs::ImageConstPtr& msg, const std::string input_frame_from_msg)
  {
    // Work on the image.
    try
    {
      // Convert the image into something opencv can handle.
      cv::Mat frame = cv_bridge::toCvShare(msg, sensor_msgs::image_encodings::BGR8)->image;

      // Messages
      opencv_apps::FlowArrayStamped flows_msg;
      flows_msg.header = msg->header;

      if( debug_view_) {
        cv::namedWindow( window_name_, cv::WINDOW_AUTOSIZE );
        if (need_config_update_) {
          reconfigure_server_->updateConfig(config_);
          need_config_update_ = false;
        }
      }

      // Do the work
      if ( frame.channels() > 1 ) {
        cv::cvtColor( frame, gray, cv::COLOR_BGR2GRAY );
      } else {
        frame.copyTo(gray);
      }
      if( prevgray.data )
      {
        cv::calcOpticalFlowFarneback(prevgray, gray, flow, 0.5, 3, 15, 3, 5, 1.2, 0);
        cv::cvtColor(prevgray, cflow, cv::COLOR_GRAY2BGR);
        //drawOptFlowMap(flow, cflow, 16, 1.5, Scalar(0, 255, 0));
        int step = 16;
        cv::Scalar color = cv::Scalar(0, 255, 0);
        for(int y = 0; y < cflow.rows; y += step)
          for(int x = 0; x < cflow.cols; x += step)
        {
          const cv::Point2f& fxy = flow.at<cv::Point2f>(y, x);
          cv::line(cflow, cv::Point(x,y), cv::Point(cvRound(x+fxy.x), cvRound(y+fxy.y)),
                   color);
          cv::circle(cflow, cv::Point(x,y), 2, color, -1);

          opencv_apps::Flow flow_msg;
          opencv_apps::Point2D point_msg;
          opencv_apps::Point2D velocity_msg;
          point_msg.x = x;
          point_msg.y = y;
          velocity_msg.x = fxy.x;
          velocity_msg.y = fxy.y;
          flow_msg.point = point_msg;
          flow_msg.velocity = velocity_msg;
          flows_msg.flow.push_back(flow_msg);
        }
      }

      std::swap(prevgray, gray);

      //-- Show what you got
      if( debug_view_) {
        cv::imshow( window_name_, cflow );
        int c = cv::waitKey(1);
      }


      // Publish the image.
      sensor_msgs::Image::Ptr out_img = cv_bridge::CvImage(msg->header, "bgr8", cflow).toImageMsg();
      img_pub_.publish(out_img);
      msg_pub_.publish(flows_msg);
    }
    catch (cv::Exception &e)
    {
      NODELET_ERROR("Image processing error: %s %s %s %i", e.err.c_str(), e.func.c_str(), e.file.c_str(), e.line);
    }

    prev_stamp_ = msg->header.stamp;
  }

  void subscribe()
  {
    NODELET_DEBUG("Subscribing to image topic.");
    if (config_.use_camera_info)
      cam_sub_ = it_->subscribeCamera("image", 3, &FBackFlowNodelet::imageCallbackWithInfo, this);
    else
      img_sub_ = it_->subscribe("image", 3, &FBackFlowNodelet::imageCallback, this);
  }

  void unsubscribe()
  {
    NODELET_DEBUG("Unsubscribing from image topic.");
    img_sub_.shutdown();
    cam_sub_.shutdown();
  }

public:
  virtual void onInit()
  {
    Nodelet::onInit();
    it_ = boost::shared_ptr<image_transport::ImageTransport>(new image_transport::ImageTransport(*nh_));

    pnh_->param("debug_view", debug_view_, false);
    if (debug_view_) {
      always_subscribe_ = true;
    }
    prev_stamp_ = ros::Time(0, 0);

    window_name_ = "flow";
    
    reconfigure_server_ = boost::make_shared<dynamic_reconfigure::Server<Config> >(*pnh_);
    dynamic_reconfigure::Server<Config>::CallbackType f =
      boost::bind(&FBackFlowNodelet::reconfigureCallback, this, _1, _2);
    reconfigure_server_->setCallback(f);

    img_pub_ = advertiseImage(*pnh_, "image", 1);
    msg_pub_ = advertise<opencv_apps::FlowArrayStamped>(*pnh_, "flows", 1);

    onInitPostProcess();
  }
};
bool FBackFlowNodelet::need_config_update_ = false;
}

#include <pluginlib/class_list_macros.h>
PLUGINLIB_EXPORT_CLASS(fback_flow::FBackFlowNodelet, nodelet::Nodelet);
