line function is not recognized [closed]

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i am working in visual studio 2015 and opencv 3.1. when i run typical code for drawing line ;

#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
#include<iostream>
using namespace cv;

int main()
{
    // Create black empty images
    Mat image = Mat::zeros(400, 400, CV_8UC3);

    // Draw a line 

    line(image, Point(15, 20), Point(70, 50), Scalar(110, 220, 0), 2, 8);

    waitKey(0);
    return(0);
}

i get the build error: identifier "line" is undefined