Add an example code for the KCF tracker

modules/tracking/samples/kcf.cpp

+/*----------------------------------------------
+ * Usage:
+ * example_tracking_kcf <video path>
+ *
+ * example:
+ * example_tracking_kcf Bolt/img/%04.jpg
+ * example_tracking_kcf faceocc2.webm
+ *--------------------------------------------------*/
+
+#include <opencv2/opencv.hpp>
+#include <opencv2/tracking.hpp>
+#include <iostream>
+#include <cstring>
+#include <algorithm>
+
+using namespace std;
+using namespace cv;
+
+class BoxExtractor {
+public:
+  Rect2d extract(Mat img);
+  Rect2d extract(const std::string& windowName, Mat img);
+
+  struct handlerT{
+    bool isDrawing;
+    Rect2d box;
+    Mat image;
+
+    // initializer list
+    handlerT(): isDrawing(false) {};
+  }params;
+
+private:
+  static void mouseHandler(int event, int x, int y, int flags, void *param);
+  void opencv_mouse_callback( int event, int x, int y, int , void *param );
+};
+
+int main( int , char** argv ){
+  BoxExtractor box;
+
+  // create the tracker
+  Ptr<Tracker> tracker = Tracker::create( "KCF" );
+
+  Rect2d roi;
+  int start_frame = 0;
+  std::string video = argv[1];
+
+  VideoCapture cap;
+  cap.open( video );
+  cap.set( CAP_PROP_POS_FRAMES, start_frame );
+
+  Mat frame;
+
+  // get bounding box
+  cap >> frame;
+  roi=box.extract("tracker",frame);
+
+  // initialize the tracker
+  tracker->init(frame,roi);
+
+  // do the tracking
+  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;
+  }
+
+}
+
+void BoxExtractor::mouseHandler(int event, int x, int y, int flags, void *param){
+    BoxExtractor *self =static_cast<BoxExtractor*>(param);
+    self->opencv_mouse_callback(event,x,y,flags,param);
+}
+
+void BoxExtractor::opencv_mouse_callback( int event, int x, int y, int , void *param ){
+    handlerT * data = (handlerT*)param;
+    switch( event ){
+      // update the selected bounding box
+      case EVENT_MOUSEMOVE:
+        if( data->isDrawing ){
+          data->box.width = x-data->box.x;
+          data->box.height = y-data->box.y;
+        }
+      break;
+
+      // start to select the bounding box
+      case EVENT_LBUTTONDOWN:
+        data->isDrawing = true;
+        data->box = cvRect( x, y, 0, 0 );
+      break;
+
+      // cleaning up the selected bounding box
+      case EVENT_LBUTTONUP:
+        data->isDrawing = false;
+        if( data->box.width < 0 ){
+          data->box.x += data->box.width;
+          data->box.width *= -1;
+        }
+        if( data->box.height < 0 ){
+          data->box.y += data->box.height;
+          data->box.height *= -1;
+        }
+      break;
+    }
+}
+
+Rect2d BoxExtractor::extract(Mat img){
+  return extract("Bounding Box Extractor", img);
+}
+
+Rect2d BoxExtractor::extract(const std::string& windowName, Mat img){
+
+  int key=0;
+
+  // show the image and give feedback to user
+  imshow(windowName,img);
+  printf("Select an object to track and then press SPACE/BACKSPACE/ENTER button!\n");
+
+  // copy the data, rectangle should be drawn in the fresh image
+  params.image=img.clone();
+
+  // select the object
+  setMouseCallback( windowName, mouseHandler, (void *)&params );
+
+  while(!(key==32 || key==27 || key==13)){
+    // draw the selected object
+    rectangle(
+      params.image,
+      Point(params.box.x, params.box.y),
+      Point(params.box.x+params.box.width,params.box.y+params.box.height),
+      Scalar(255,0,0),2,1
+    );
+
+    // show the image bouding box
+    imshow(windowName,params.image);
+
+    // reset the image
+    params.image=img.clone();
+
+    //get keyboard event
+    key=waitKey(1);
+  }
+
+
+  return params.box;
+}
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