OpenCV/opencv_contrib/modules/tracking/samples/tutorial_customizing_cn_tracker.cpp

#include <opencv2/core/utility.hpp>
#include <opencv2/tracking.hpp>
#include <opencv2/videoio.hpp>
#include <opencv2/highgui.hpp>
#include <iostream>
#include <cstring>
#include "samples_utility.hpp"

using namespace std;
using namespace cv;

// prototype of the functino for feature extractor
void sobelExtractor(const Mat img, const Rect roi, Mat& feat);

int main( int argc, char** argv ){
  // show help
  if(argc<2){
    cout<<
      " Usage: tracker <video_name>\n"
      " examples:\n"
      " example_tracking_kcf Bolt/img/%04d.jpg\n"
      " example_tracking_kcf faceocc2.webm\n"
      << endl;
    return 0;
  }

  // declares all required variables
  Rect roi;
  Mat frame;

  //! [param]
  TrackerKCF::Params param;
  param.desc_pca = TrackerKCF::GRAY | TrackerKCF::CN;
  param.desc_npca = 0;
  param.compress_feature = true;
  param.compressed_size = 2;
  //! [param]

  // create a tracker object
  //! [create]
  Ptr<TrackerKCF> tracker = TrackerKCF::create(param);
  //! [create]

  //! [setextractor]
  tracker->setFeatureExtractor(sobelExtractor);
  //! [setextractor]

  // set input video
  std::string video = argv[1];
  VideoCapture cap(video);

  // get bounding box
  cap >> frame;
  roi=selectROI("tracker",frame);

  //quit if ROI was not selected
  if(roi.width==0 || roi.height==0)
    return 0;

  // initialize the tracker
  tracker->init(frame,roi);

  // perform the tracking process
  printf("Start the tracking process, press ESC to quit.\n");
  for ( ;; ){
    // get frame from the video
    cap >> frame;

    // stop the program if no more images
    if(frame.rows==0 || frame.cols==0)
      break;

    // update the tracking result
    tracker->update(frame,roi);

    // draw the tracked object
    rectangle( frame, roi, Scalar( 255, 0, 0 ), 2, 1 );

    // show image with the tracked object
    imshow("tracker",frame);

    //quit on ESC button
    if(waitKey(1)==27)break;
  }

  return 0;
}

void sobelExtractor(const Mat img, const Rect roi, Mat& feat){
    Mat sobel[2];
    Mat patch;
    Rect region=roi;

    //! [insideimage]
    // extract patch inside the image
    if(roi.x<0){region.x=0;region.width+=roi.x;}
    if(roi.y<0){region.y=0;region.height+=roi.y;}
    if(roi.x+roi.width>img.cols)region.width=img.cols-roi.x;
    if(roi.y+roi.height>img.rows)region.height=img.rows-roi.y;
    if(region.width>img.cols)region.width=img.cols;
    if(region.height>img.rows)region.height=img.rows;
    //! [insideimage]

    patch=img(region).clone();
    cvtColor(patch,patch, COLOR_BGR2GRAY);

    //! [padding]
    // add some padding to compensate when the patch is outside image border
    int addTop,addBottom, addLeft, addRight;
    addTop=region.y-roi.y;
    addBottom=(roi.height+roi.y>img.rows?roi.height+roi.y-img.rows:0);
    addLeft=region.x-roi.x;
    addRight=(roi.width+roi.x>img.cols?roi.width+roi.x-img.cols:0);

    copyMakeBorder(patch,patch,addTop,addBottom,addLeft,addRight,BORDER_REPLICATE);
    //! [padding]

    //! [sobel]
    Sobel(patch, sobel[0], CV_32F,1,0,1);
    Sobel(patch, sobel[1], CV_32F,0,1,1);

    merge(sobel,2,feat);
    //! [sobel]

    //! [postprocess]
    feat=feat/255.0-0.5; // normalize to range -0.5 .. 0.5
    //! [postprocess]
}