samples/cpp/lkdemo.cpp

使用 Lucas-Kanade 光流算法的示例

#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()
{
    // 打印欢迎信息和 OpenCV 版本
cout << "\n这是一个使用 Lucas-Kanade 光流算法的示例 lkdemo()，\n"
            "使用 OpenCV 版本 " << CV_VERSION << endl;
cout << "\n默认使用相机，但您可以提供视频路径作为参数。\n";
cout << "\n热键：\n"
            "\tESC - 退出程序\n"
            "\tr - 自动初始化跟踪\n"
            "\tc - 删除所有点\n"
            "\tn - 切换“夜间”模式\n"
            "要添加/删除特征点，请单击它\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 << "无法初始化捕获...\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 )
        {
            // 自动初始化
            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;
}