added tutorials for KCF tracker

modules/tracking/samples/tutorial_introduction_to_tracker.cpp

@@ -0,0 +1,87 @@
+#include <opencv2/core/utility.hpp>
+#include <opencv2/tracking.hpp>
+#include <opencv2/videoio.hpp>
+#include <opencv2/highgui.hpp>
+#include <iostream>
+#include <cstring>
+
+using namespace std;
+using namespace cv;
+
+int main( int argc, char** argv ){
+  // show help
+  //! [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;
+  }
+  //! [help]
+
+  // declares all required variables
+  //! [vars]
+  Rect2d roi;
+  Mat frame;
+  //! [vars]
+
+  // create a tracker object
+  //! [create]
+  Ptr<Tracker> tracker = Tracker::create( "KCF" );
+  //! [create]
+
+  // set input video
+  //! [setvideo]
+  std::string video = argv[1];
+  VideoCapture cap(video);
+  //! [setvideo]
+
+  // get bounding box
+  //! [getframe]
+  cap >> frame;
+  //! [getframe]
+  //! [selectroi]
+  roi=selectROI("tracker",frame);
+  //! [selectroi]
+
+  //quit if ROI was not selected
+  if(roi.width==0 || roi.height==0)
+    return 0;
+
+  // initialize the tracker
+  //! [init]
+  tracker->init(frame,roi);
+  //! [init]
+
+  // 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
+    //! [update]
+    tracker->update(frame,roi);
+    //! [update]
+
+    //! [visualization]
+    // draw the tracked object
+    rectangle( frame, roi, Scalar( 255, 0, 0 ), 2, 1 );
+
+    // show image with the tracked object
+    imshow("tracker",frame);
+    //! [visualization]
+
+    //quit on ESC button
+    if(waitKey(1)==27)break;
+  }
+
+  return 0;
+}