samples/cpp/lkdemo.cpp

   1 #include "opencv2/video/tracking.hpp"
   2 #include "opencv2/imgproc/imgproc.hpp"
   3 #include "opencv2/videoio/videoio.hpp"
   4 #include "opencv2/highgui/highgui.hpp"
   5
   6 #include <iostream>
   7 #include <ctype.h>
   8
   9 using namespace cv;
  10 using namespace std;
  11
  12 static void help()
  13 {
  14     // print a welcome message, and the OpenCV version
  15     cout << "\nThis is a demo of Lukas-Kanade optical flow lkdemo(),\n"
  16             "Using OpenCV version " << CV_VERSION << endl;
  17     cout << "\nIt uses camera by default, but you can provide a path to video as an argument.\n";
  18     cout << "\nHot keys: \n"
  19             "\tESC - quit the program\n"
  20             "\tr - auto-initialize tracking\n"
  21             "\tc - delete all the points\n"
  22             "\tn - switch the \"night\" mode on/off\n"
  23             "To add/remove a feature point click it\n" << endl;
  24 }
  25
  26 Point2f point;
  27 bool addRemovePt = false;
  28
  29 static void onMouse( int event, int x, int y, int /*flags*/, void* /*param*/ )
  30 {
  31     if( event == EVENT_LBUTTONDOWN )
  32     {
  33         point = Point2f((float)x, (float)y);
  34         addRemovePt = true;
  35     }
  36 }
  37
  38 int main( int argc, char** argv )
  39 {
  40     help();
  41
  42     VideoCapture cap;
  43     TermCriteria termcrit(TermCriteria::COUNT|TermCriteria::EPS,20,0.03);
  44     Size subPixWinSize(10,10), winSize(31,31);
  45
  46     const int MAX_COUNT = 500;
  47     bool needToInit = false;
  48     bool nightMode = false;
  49
  50     if( argc == 1 || (argc == 2 && strlen(argv[1]) == 1 && isdigit(argv[1][0])))
  51         cap.open(argc == 2 ? argv[1][0] - '0' : 0);
  52     else if( argc == 2 )
  53         cap.open(argv[1]);
  54
  55     if( !cap.isOpened() )
  56     {
  57         cout << "Could not initialize capturing...\n";
  58         return 0;
  59     }
  60
  61     namedWindow( "LK Demo", 1 );
  62     setMouseCallback( "LK Demo", onMouse, 0 );
  63
  64     Mat gray, prevGray, image;
  65     vector<Point2f> points[2];
  66
  67     for(;;)
  68     {
  69         Mat frame;
  70         cap >> frame;
  71         if( frame.empty() )
  72             break;
  73
  74         frame.copyTo(image);
  75         cvtColor(image, gray, COLOR_BGR2GRAY);
  76
  77         if( nightMode )
  78             image = Scalar::all(0);
  79
  80         if( needToInit )
  81         {
  82             // automatic initialization
  83             goodFeaturesToTrack(gray, points[1], MAX_COUNT, 0.01, 10, Mat(), 3, 0, 0.04);
  84             cornerSubPix(gray, points[1], subPixWinSize, Size(-1,-1), termcrit);
  85             addRemovePt = false;
  86         }
  87         else if( !points[0].empty() )
  88         {
  89             vector<uchar> status;
  90             vector<float> err;
  91             if(prevGray.empty())
  92                 gray.copyTo(prevGray);
  93             calcOpticalFlowPyrLK(prevGray, gray, points[0], points[1], status, err, winSize,
  94                                  3, termcrit, 0, 0.001);
  95             size_t i, k;
  96             for( i = k = 0; i < points[1].size(); i++ )
  97             {
  98                 if( addRemovePt )
  99                 {
 100                     if( norm(point - points[1][i]) <= 5 )
 101                     {
 102                         addRemovePt = false;
 103                         continue;
 104                     }
 105                 }
 106
 107                 if( !status[i] )
 108                     continue;
 109
 110                 points[1][k++] = points[1][i];
 111                 circle( image, points[1][i], 3, Scalar(0,255,0), -1, 8);
 112             }
 113             points[1].resize(k);
 114         }
 115
 116         if( addRemovePt && points[1].size() < (size_t)MAX_COUNT )
 117         {
 118             vector<Point2f> tmp;
 119             tmp.push_back(point);
 120             cornerSubPix( gray, tmp, winSize, Size(-1,-1), termcrit);
 121             points[1].push_back(tmp[0]);
 122             addRemovePt = false;
 123         }
 124
 125         needToInit = false;
 126         imshow("LK Demo", image);
 127
 128         char c = (char)waitKey(10);
 129         if( c == 27 )
 130             break;
 131         switch( c )
 132         {
 133         case 'r':
 134             needToInit = true;
 135             break;
 136         case 'c':
 137             points[0].clear();
 138             points[1].clear();
 139             break;
 140         case 'n':
 141             nightMode = !nightMode;
 142             break;
 143         }
 144
 145         std::swap(points[1], points[0]);
 146         cv::swap(prevGray, gray);
 147     }
 148
 149     return 0;
 150 }