c++ - 对 cv::calcOpticalFlowPyrLK 的 undefined reference

Question

我现在正在学习 OpenCV，并且正在测试可用的 LK 演示程序。我是编程新手，所以我不知道出了什么问题。

我遇到了这些问题:

C:\Qt\projects\build-lkdemo-Desktop_Qt_5_3_MinGW_32bit-Debug\debug\main.o:-1: In function `Z5qMainiPPc':
C:\Qt\projects\lkdemo\main.cpp:96: error: undefined reference to `cv::calcOpticalFlowPyrLK(cv::_InputArray const&, cv::_InputArray const&, cv::_InputArray const&, cv::_OutputArray const&, cv::_OutputArray const&, cv::_OutputArray const&, cv::Size_<int>, int, cv::TermCriteria, int, double)'
collect2.exe:-1: error: error: ld returned 1 exit status

代码如下:

#include <QApplication>
#include "opencv2/video/tracking.hpp"
#include "opencv2/imgproc/imgproc.hpp"
#include "opencv2/highgui/highgui.hpp"

#include <iostream>
#include <ctype.h>

using namespace cv;
using namespace std;

static void help()
{
    // print a welcome message, and the OpenCV version
    cout << "\nThis is a demo of Lukas-Kanade optical flow lkdemo(),\n"
            "Using OpenCV version %s\n" << CV_VERSION << "\n"
            << endl;

    cout << "\nHot keys: \n"
            "\tESC - quit the program\n"
            "\tr - auto-initialize tracking\n"
            "\tc - delete all the points\n"
            "\tn - switch the \"night\" mode on/off\n"
            "To add/remove a feature point click it\n" << endl;
}

Point2f point;
bool addRemovePt = false;

static void onMouse( int event, int x, int y, int /*flags*/, void* /*param*/ )
{
    if( event == CV_EVENT_LBUTTONDOWN )
    {
        point = Point2f((float)x,(float)y);
        addRemovePt = true;
    }
}

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    VideoCapture cap;
    TermCriteria termcrit(CV_TERMCRIT_ITER|CV_TERMCRIT_EPS,20,0.03);
    Size subPixWinSize(10,10), winSize(31,31);

    const int MAX_COUNT = 500;
    bool needToInit = false;
    bool nightMode = false;

    if( argc == 1 || (argc == 2 && strlen(argv[1]) == 1 && isdigit(argv[1][0])))
        cap.open(argc == 2 ? argv[1][0] - '0' : 0);
    else if( argc == 2 )
        cap.open(argv[1]);

    if( !cap.isOpened() )
    {
        cout << "Could not initialize capturing...\n";
        return a.exec();
    }

    help();

    namedWindow( "LK Demo", 1 );
    setMouseCallback( "LK Demo", onMouse, 0 );

    Mat gray, prevGray, image;
    vector<Point2f> points[2];

    for(;;)
    {
        Mat frame;
        cap >> frame;
        if( frame.empty() )
            break;

        frame.copyTo(image);
        cvtColor(image, gray, CV_BGR2GRAY);

        if( nightMode )
            image = Scalar::all(0);

        if( needToInit )
        {
            // automatic initialization
            goodFeaturesToTrack(gray, points[1], MAX_COUNT, 0.01, 10, Mat(), 3, 0, 0.04);
            cornerSubPix(gray, points[1], subPixWinSize, Size(-1,-1), termcrit);
            addRemovePt = false;
        }
        else if( !points[0].empty() )
        {
            vector<uchar> status;
            vector<float> err;
            if(prevGray.empty())
                gray.copyTo(prevGray);
            calcOpticalFlowPyrLK(prevGray, gray, points[0], points[1], status, err, winSize,
                                 3, termcrit, 0, 0.001);
            size_t i, k;
            for( i = k = 0; i < points[1].size(); i++ )
            {
                if( addRemovePt )
                {
                    if( norm(point - points[1][i]) <= 5 )
                    {
                        addRemovePt = false;
                        continue;
                    }
                }

                if( !status[i] )
                    continue;

                points[1][k++] = points[1][i];
                circle( image, points[1][i], 3, Scalar(0,255,0), -1, 8);
            }
            points[1].resize(k);
        }

        if( addRemovePt && points[1].size() < (size_t)MAX_COUNT )
        {
            vector<Point2f> tmp;
            tmp.push_back(point);
            cornerSubPix( gray, tmp, winSize, cvSize(-1,-1), termcrit);
            points[1].push_back(tmp[0]);
            addRemovePt = false;
        }

        needToInit = false;
        imshow("LK Demo", image);

        char c = (char)waitKey(10);
        if( c == 27 )
            break;
        switch( c )
        {
        case 'r':
            needToInit = true;
            break;
        case 'c':
            points[1].clear();
            break;
        case 'n':
            nightMode = !nightMode;
            break;
        default:
            ;
        }

        std::swap(points[1], points[0]);
        swap(prevGray, gray);
    }

    return a.exec();
}

我需要知道什么来解决这个问题吗？

编辑 1: 这是我的 .pro:

#-------------------------------------------------
#
# Project created by QtCreator 2015-02-26T10:12:31
#
#-------------------------------------------------

INCLUDEPATH += C:\opencv-mingw\install\include
LIBS += -L"C:/opencv-mingw/install/x64/mingw/bin"
LIBS += -lopencv_core249 -lopencv_highgui249 -lopencv_imgproc249

QT       += core gui

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

TARGET = lkdemo
TEMPLATE = app


SOURCES += main.cpp

Answer 1

cv::calcOpticalFlowPyrLK()是video模块的一部分。您应该将 opencv_videoXXXXd.lib 和/或 opencv_videoXXXX.lib 添加到链接器。

即:

LIBS += -lopencv_core249 -lopencv_highgui249 -lopencv_imgproc249 -lopencv_video249