光流opencv中的错误

我试图在两张图像中找到光流。我的代码给出以下2个错误：

error LNK1120: 1 unresolved externals
error LNK2019: unresolved external symbol "void __cdecl cv::calcOpticalFlowPyrLK(
class cv::_InputArray const &,class cv::_InputArray const &,class cv::_InputArray 
const &,class cv::_OutputArray const &,class cv::_OutputArray const &,class 
cv::_OutputArray const &,class cv::Size_<int>,int,class cv::TermCriteria,double,
int)"(?calcOpticalFlowPyrLK@cv@@YAXABV_InputArray@1@00ABV_OutputArray@1@11V?$Size_
@H@1@HVTermCriteria@1@NH@Z) referenced in function "public: void __thiscall 
optical_flow::optical(void)" (?optical@optical_flow@@QAEXXZ)

代码如下所示。请帮我解决这个错误。如果我注释调用calcOpticalFlowPyrLK函数的行，我找不到原因。它停止给出此错误。

void optical()
    {   
    // Load two images and allocate other structures
        Mat imgA = imread("a.jpg", CV_LOAD_IMAGE_GRAYSCALE);
        Mat imgB = imread("c.jpg", CV_LOAD_IMAGE_GRAYSCALE);
        Size img_sz = imgA.size();
        Mat imgC(img_sz,1);
        int win_size = 15;
        int maxCorners = 20;
        double qualityLevel = 0.05;
        double minDistance = 5.0;
        int blockSize = 3;
        double k = 0.04;
        std::vector<cv::Point2f> cornersA;
        cornersA.reserve(maxCorners);
        std::vector<cv::Point2f> cornersB;
        cornersB.reserve(maxCorners);
        goodFeaturesToTrack( imgA,cornersA,maxCorners,qualityLevel,minDistance,cv::Mat());
        goodFeaturesToTrack( imgB,cornersB,maxCorners,qualityLevel,minDistance,cv::Mat());
        cout<<"Runniung"<<endl;
        cornerSubPix( imgA, cornersA, Size( win_size, win_size ), Size( -1, -1 ),
        TermCriteria( CV_TERMCRIT_ITER | CV_TERMCRIT_EPS, 20, 0.03 ) );
        cornerSubPix( imgB, cornersB, Size( win_size, win_size ), Size( -1, -1 ),
        TermCriteria( CV_TERMCRIT_ITER | CV_TERMCRIT_EPS, 20, 0.03 ) );
        // Call Lucas Kanade algorithm
        CvSize pyr_sz = Size( img_sz.width+8, img_sz.height/3 );
        std::vector<uchar> features_found;
        features_found.reserve(maxCorners);
        std::vector<float> feature_errors;
        feature_errors.reserve(maxCorners);
        calcOpticalFlowPyrLK( imgA, imgB, cornersA, cornersB, features_found, feature_errors ,Size( win_size, win_size ), 5,cvTermCriteria( CV_TERMCRIT_ITER | CV_TERMCRIT_EPS, 20, 0.3 ), 0 );
        // Make an image of the results

        for( int i=0; i < features_found.size(); i++ ){
         cout<<"Error is "<<feature_errors[i]<<endl;
         //continue;
         cout<<"Got it"<<endl;
         Point p0( ceil( cornersA[i].x ), ceil( cornersA[i].y ) );
         Point p1( ceil( cornersB[i].x ), ceil( cornersB[i].y ) );
         line( imgC, p0, p1, CV_RGB(255,255,255), 2 );
         }

         namedWindow( "ImageA", 0 );
         namedWindow( "ImageB", 0 );
         namedWindow( "LKpyr_OpticalFlow", 0 );

         imshow( "ImageA", imgA );
         imshow( "ImageB", imgB );
         imshow( "LKpyr_OpticalFlow", imgC );
         cvWaitKey(0);
        // return 0;
        //return 0;
    }
int _tmain(int argc, _TCHAR* argv[])
{
//  video obj("video.avi");
    optical_flow obj2;
    obj2.optical();
}