OpenCV C++ point tracking technology

Procedure description

// Program description: From the official sample program-point tracking technology demonstration in the Samples folder under the OpenCV installation directory
// Source code path: opencv\sources\samples\cpp\lkdemo.cpp
// Operating system: Windows 10 64bit
// Development Language: C++
// IDE version: Visual Studio 2019
// OpenCV version: 4.20

Code

#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() -该Demo演示了 Lukas-Kanade基于光流的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 -程序默认从摄像头读入视频，可以按需改为从视频文件读入图像.\n";
    cout << "\nHot keys: \n"
        "\tESC - quit the program - 退出程序\n"
        "\tr - auto-initialize tracking -自动进行追踪\n"
        "\tc - delete all the points - 删除所有点\n"
        "\tn - switch the \"night\" mode on/off - 开/光-夜晚模式\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();
    //这里打开本地视频，也可以调用摄像头视频
    //cap.open(0);
    cap.open("100.mp4");

    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, 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;
}

Operating instructions and operating results

Operating instructions You

can call the camera video, you can also read the local video; the following is to read a local video, click to track the effect of the


original video link https://www.bilibili.com/video/BV19t4y197Qz