OpenCV LK光流法测试

OpenCV版本： 3.2.0

例程文件目录/samples/cpp/lkdemo.cpp

原始程序是采集相机数据，台式机没有摄像头，用Euroc测试集，偷ORB_SLAM2 /Examples/Monocular/mono_euroc.cc里的LoadImages函数读取数据

在cpp目录下新建一个自己的目录mylk，拷贝lkdemo和example_cmake目录下的CMakeLists.txt并修改：

add_executable(lk_example lkdemo.cpp)
target_link_libraries(lk_example ${OpenCV_LIBS})

新建目录build，进入后cmake .. + make 编译运行即可。run.sh如下:

./lkdemo ~/slamData/EuRoC/mav02/cam0/data ~/ORB_SLAM2/Examples/Stereo/EuRoC_TimeStamps/MH02.txt

先提取角点，亚像素精度提炼角点，光流跟踪。

运行过程中会监控鼠标和键盘：

按下鼠标左键 -> 添加一个角点

按下r -> 初始化角点

按下c -> 清除角点

按下n -> 只显示角点（右图）

按下esc -> 退出

修改后的程序：

 #include "opencv2/video/tracking.hpp"
 #include "opencv2/imgproc.hpp"
 #include "opencv2/videoio.hpp"
 #include "opencv2/highgui.hpp"

 #include <iostream>
 #include <ctype.h>
 #include <fstream>
 #include <algorithm>
 using namespace std;

 using namespace cv;
 void LoadImages(const string &strImagePath, const string &strPathTimes,
                 vector<string> &vstrImages, vector<double> &vTimeStamps)
 {
     ifstream fTimes;
     fTimes.open(strPathTimes.c_str());
     vTimeStamps.reserve();
     vstrImages.reserve();
     while(!fTimes.eof())
     {
         string s;
         getline(fTimes,s);
         if(!s.empty())
         {
             stringstream ss;
             ss << s;
             vstrImages.push_back(strImagePath + "/" + ss.str() + ".png");
             double t;
             ss >> t;
             vTimeStamps.push_back(t/1e9);

         }
     }
 }
 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 " << CV_VERSION << endl;
     cout << "\nIt uses camera by default, but you can provide a path to video as an argument.\n";
     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 == EVENT_LBUTTONDOWN )
     {
         point = Point2f((float)x, (float)y);
         addRemovePt = true;
     }
 }

 int main( int argc, char** argv )
 {
     VideoCapture cap;
     TermCriteria termcrit(TermCriteria::COUNT|TermCriteria::EPS,,0.03);
     Size subPixWinSize(,), winSize(,);

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

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

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

     vector<string> vstrImageFilenames;
     vector<double> vstrstamps;
     LoadImages(string(argv[]), string(argv[]), vstrImageFilenames, vstrstamps);
     for(int i=;i<vstrImageFilenames.size();i++)
     {

         image = imread(vstrImageFilenames[i],IMREAD_COLOR);
         cvtColor(image, gray, COLOR_BGR2GRAY);

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

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

                 if( !status[i] )
                     continue;

                 points[][k++] = points[][i];
                 circle( image, points[][i], , Scalar(,,), -, );
             }
             points[].resize(k);
         }

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

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

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

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

     return ;
 }

参考：goodFeaturesToTrack函数详细注释