include<opencv2/opencv.hpp>

include<iostream>

include<vector>

int main(int argc, char *argv[])

{

cv::Mat frame;
cv::Mat back;
cv::Mat fore;
cv::VideoCapture cap(0);
cv::BackgroundSubtractorMOG2 bg;
bg.set("nmixtures" , 3);
bg.set("bShadowDetection", false);

std::vector<std::vector<cv::Point> > contours;

cv::namedWindow("Frame");
cv::namedWindow("Background");

for (;;)
{
    cap >> frame;
    bg.operator ()(frame, fore);
    bg.getBackgroundImage(back);
    cv::erode(fore, fore, cv::Mat());
    cv::dilate(fore, fore, cv::Mat());
    cv::findContours(fore, contours, CV_RETR_EXTERNAL, CV_CHAIN_APPROX_NONE);
    cv::drawContours(frame, contours, -1, cv::Scalar(0, 0, 255), 2);
    cv::imshow("Frame", frame);
    cv::imshow("Background", back);
    if (cv::waitKey(30) >= 0) break;
}
return 0;

}

error : error C3861: normHamming: identifier not found c:\program files\opencv\build\include\opencv2\features2d\features2d.hpp

#include <opencv2/opencv.hpp>
#include <iostream>
#include <vector>


int main(int argc, char *argv[])

{

    cv::Mat frame;
    cv::Mat back;
    cv::Mat fore;
    cv::VideoCapture cap(0);
    cv::BackgroundSubtractorMOG2 bg;
    bg.set("nmixtures" , 3);
    bg.set("bShadowDetection", false);

    std::vector<std::vector<cv::Point> > contours;

    cv::namedWindow("Frame");
    cv::namedWindow("Background");

    for (;;)
    {
        cap >> frame;
        bg.operator ()(frame, fore);
        bg.getBackgroundImage(back);
        cv::erode(fore, fore, cv::Mat());
        cv::dilate(fore, fore, cv::Mat());
        cv::findContours(fore, contours, CV_RETR_EXTERNAL, CV_CHAIN_APPROX_NONE);
        cv::drawContours(frame, contours, -1, cv::Scalar(0, 0, 255), 2);
        cv::imshow("Frame", frame);
        cv::imshow("Background", back);
        if (cv::waitKey(30) >= 0) break;
    }
    return 0;
}


error : error C3861: normHamming: identifier not found  c:\program files\opencv\build\include\opencv2\features2d\features2d.hpp