CV_EXPORTS_W void calcOpticalFlowPyrLK( InputArray prevImg, InputArray nextImg,

InputArray prevPts, InputOutputArray nextPts,

OutputArray status, OutputArray err,

Size winSize = Size(21,21), int maxLevel = 3,

TermCriteria criteria = TermCriteria(TermCriteria::COUNT+TermCriteria::EPS, 30, 0.01),

int flags = 0, double minEigThreshold = 1e-4 );

#include "opencv2/video/tracking.hpp"

#include "opencv2/imgproc.hpp"

#include "opencv2/videoio.hpp"

#include "opencv2/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 " << 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,20,0.03);

Size subPixWinSize(10,10), winSize(31,31);

const int MAX_COUNT = 500;

bool needToInit = false;

bool nightMode = false;

help();

cv::CommandLineParser parser(argc, argv, "{@input|0|}");

string input = parser.get<string>("@input");

if( input.size() == 1 && isdigit(input[0]) )

cap.open(input[0] - '0');

else

cap.open(input);

if( !cap.isOpened() )

{

cout << "Could not initialize capturing...\n";

return 0;

}

namedWindow( "LK Demo", 1 );

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

Mat gray, prevGray, image, frame;

vector<Point2f> points[2];

for(;;)

{

cap >> frame;

if( frame.empty() )

break;

frame.copyTo(image);

cvtColor(image, gray, COLOR_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, Size(-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[0].clear();

points[1].clear();

break;

case 'n':

nightMode = !nightMode;

break;

}

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

cv::swap(prevGray, gray);

}

return 0;

}