createBackgroundSubtractorMOG2(int history=500, double varThreshold=16,bool detectShadows=true);

createBackgroundSubtractorKNN(int history=500, double dist2Threshold=400.0, bool detectShadows=true);

#include<opencv2/opencv.hpp>
using namespace cv;

int main()
{
  VideoCapture capture;
  capture.open("E:/image/01.avi");
  if(!capture.isOpened())
  {
    printf("can not open video file  \n");
    return -1;
  }
  Mat frame;
  namedWindow("input", CV_WINDOW_AUTOSIZE);
  namedWindow("MOG2", CV_WINDOW_AUTOSIZE);
  namedWindow("KNN", CV_WINDOW_AUTOSIZE);
  Mat maskMOG2, maskKNN;
  Ptr<BackgroundSubtractor> pMOG2 = createBackgroundSubtractorMOG2(500,25,true);
  Ptr<BackgroundSubtractor> pKNN = createBackgroundSubtractorKNN();

  Mat kernel = getStructuringElement(MORPH_RECT, Size(5,5));
  while (capture.read(frame))
  {
    imshow("input", frame);

    pMOG2->apply(frame, maskMOG2);
    pKNN->apply(frame, maskKNN);
    //對處理后的幀進行開操作，減少視頻中較小的波動造成的影響
    morphologyEx(maskMOG2,maskMOG2, MORPH_OPEN, kernel, Point(-1,-1));
    morphologyEx(maskKNN,maskKNN, MORPH_OPEN, kernel, Point(-1,-1));

    imshow("MOG2", maskMOG2);
    imshow("KNN", maskKNN);
    waitKey(3);
  }

  capture.release();
  return 0;

}