参考:
(70条消息) 什么是光流法_张年糕慢慢走的博客-CSDN博客_光流法
(70条消息) 计算机视觉--光流法(optical flow)简介_T-Jhon的博客-CSDN博客_光流法
此外,还有基于均值迁移的目标追踪方法:
camshift:
(75条消息) opencv3中camshift详解(一)camshiftdemo代码详解_夏言谦的博客-CSDN博客
meanshift:
(75条消息) Opencv——用均值平移法meanshift做目标追踪_走过,莫回头的博客-CSDN博客
光流法:
void cv::calcOpticalFlowPyrLK ( InputArray prevImg,InputArray nextImg,InputArray prevPts,InputOutputArray nextPts,OutputArray status,OutputArray err,Size winSize = Size(21, 21),int maxLevel = 3,TermCriteria criteria int flags = 0,double minEigThreshold = 1e-4 ) criteria = TermCriteria(TermCriteria::COUNT+TermCriteria::EPS, 30, 0.01)
prevImg ——前一帧图像。
nextImg ——后一帧图像。
prevPts ——前一帧的角点vector,初始需要输入预获取的角点。
nextPts ——后一帧的角点vector
status——output status vector (of unsigned chars); each element of the vector is set to 1 if the flow for the corresponding features has been found, otherwise, it is set to 0.
err ——输出的角点的错误信息。
winSize ——光流法窗口大小。
maxLevel——光流层数,0只有1层,1为2层,以此类推
criteria ——停止条件
flags ——operation flags:
OPTFLOW_USE_INITIAL_FLOW uses initial estimations, stored in nextPts; if the flag is not set, then prevPts is copied to nextPts and is considered the initial estimate.
OPTFLOW_LK_GET_MIN_EIGENVALS use minimum eigen values as an error measure (see minEigThreshold description); if the flag is not set, then L1 distance between patches around the original and a moved point, divided by number of pixels in a window, is used as a error measure.
minEigThreshold——the algorithm calculates the minimum eigen value of a 2x2 normal matrix of optical flow equations (this matrix is called a spatial gradient matrix in [25]), divided by number of pixels in a window; if this value is less than minEigThreshold, then a corresponding feature is filtered out and its flow is not processed, so it allows to remove bad points and get a performance boost.
定义停止条件:当迭代10次不需要计算,两次的计算结果差小于0.01也不需要计算
TermCriteria criteria = TermCriteria(TermCriteria::COUNT + TermCriteria::EPS, 10, 0.01);
稠密光流法:
void cv::calcOpticalFlowFarneback ( InputArray prev,InputArray next,InputOutputArray flow,double pyr_scale,int levels,int winsize,int iterations,int poly_n,double poly_sigma,int flags )
flow——输出的光流场数据Mat_
对象
pyr_scale——金字塔前后层大小之比,一般取0.5.
levels ——光流金字塔层数,一般取3.
iterations ——迭代次数。
poly_n ——多项式阶数 , typically poly_n =5 or 7.
poly_sigma ——standard deviation of the Gaussian that is used to smooth derivatives used as a basis for the polynomial expansion; for poly_n=5, you can set poly_sigma=1.1, for poly_n=7, a good value would be poly_sigma=1.5.
camshift:
RotatedRect cv::CamShift ( InputArray probImage,Rect & window,TermCriteria criteria )
window——Initial search window.
meanshift:
int cv::meanShift ( InputArray probImage,Rect & window,TermCriteria criteria )
光流法:
void QuickDemo::shade_flow()
{VideoCapture capture("https://vd4.bdstatic.com/mda-nm67dtz2afxmwat7/sc/cae_h264/1670390212002064886/mda-nm67dtz2afxmwat7.mp4?v_from_s=hkapp-haokan-hbf&auth_key=1670484546-0-0-792e5c9ffc23b54e025e91106b771e99&bcevod_channel=searchbox_feed&cd=0&pd=1&pt=3&logid=3546818474&vid=6396276202448861552&abtest=104960_2&klogid=3546818474");if (capture.isOpened()) {cout << "ok!" << endl;}//获取合适帧率int fps = capture.get(CAP_PROP_FPS);cout << "fps" << fps << endl;Mat old_frame, old_gray;capture.read(old_frame);cvtColor(old_frame, old_gray, COLOR_BGR2GRAY);//角点获取vector feature_pts;goodFeaturesToTrack(old_gray, feature_pts, 100, 0.01,10,Mat(),3,false);Mat frame, gray;vector pts[2];pts[0].insert(pts[0].end(), feature_pts.begin(), feature_pts.end());vector status;vector err;//定义停止条件,当迭代10次不需要计算,两次的计算结果差小于0.01也不需要计算TermCriteria criteria = TermCriteria(TermCriteria::COUNT + TermCriteria::EPS, 10, 0.01);while (true){//capture >> frame;//尽量不用//逐帧传入视频bool ret = capture.read(frame);if (!ret)break;cvtColor(frame, gray, COLOR_BGR2GRAY);//光流法函数calcOpticalFlowPyrLK(old_frame, frame, pts[0], pts[1], status, err, Size(21, 21), 3, criteria, 0);//检测是否出错size_t i = 0, k = 0;RNG rng(12345);for (i = 0; i < pts[1].size(); ++i) {//距离与状态检测if (status[i]) {pts[0][k] = pts[0][i];pts[1][k++] = pts[1][i];int b = rng.uniform(0, 255);int g = rng.uniform(0, 255);int r = rng.uniform(0, 255);circle(frame, pts[1][i], 3, Scalar(b, g, r), 3, 8);line(frame, pts[0][i], pts[1][i], Scalar(b, g, r), 3, 8);}}//更新角点vector容量pts[0].resize(k);pts[1].resize(k);imshow("frame", frame);char c = waitKey(fps+10);if (c == 27)break;//更换帧图像,帧角点信息swap(pts[1], pts[0]);swap(old_gray, gray);}capture.release();
}
稀疏光流法:
void QuickDemo::poor_shade_flow()
{VideoCapture capture("https://vd4.bdstatic.com/mda-nm67dtz2afxmwat7/sc/cae_h264/1670390212002064886/mda-nm67dtz2afxmwat7.mp4?v_from_s=hkapp-haokan-hbf&auth_key=1670484546-0-0-792e5c9ffc23b54e025e91106b771e99&bcevod_channel=searchbox_feed&cd=0&pd=1&pt=3&logid=3546818474&vid=6396276202448861552&abtest=104960_2&klogid=3546818474");if (capture.isOpened()) {cout << "ok!" << endl;}//获取合适帧率int fps = capture.get(CAP_PROP_FPS);cout << "fps" << fps << endl;Mat old_frame, old_gray;capture.read(old_frame);cvtColor(old_frame, old_gray, COLOR_BGR2GRAY);//角点光源初始化vector feature_pts;goodFeaturesToTrack(old_gray, feature_pts, 50, 0.01, 50, Mat(), 3, false);vector pts[2];pts[0].insert(pts[0].end(), feature_pts.begin(), feature_pts.end());vector initial_points;initial_points.insert(initial_points.end(), feature_pts.begin(), feature_pts.end());Mat frame, gray;vector status;vector err;//定义停止条件,当迭代10次不需要计算,两次的计算结果差小于0.01也不需要计算TermCriteria criteria = TermCriteria(TermCriteria::COUNT + TermCriteria::EPS, 10, 0.01);while (true){//capture >> frame;//尽量不用//逐帧传入视频bool ret = capture.read(frame);if (!ret)break;cvtColor(frame, gray, COLOR_BGR2GRAY);//光流法函数calcOpticalFlowPyrLK(old_frame, frame, pts[0], pts[1], status, err, Size(21, 21), 3, criteria, 0);//检测是否出错size_t i = 0, k = 0;RNG rng(12345);for (i = 0; i < pts[1].size(); ++i) {//距离与状态检测double dist = abs(pts[0][i].x - pts[1][i].x) + abs(pts[0][i].y - pts[1][i].y);if (status[i] && dist >2) {pts[0][k] = pts[0][i];pts[1][k++] = pts[1][i];initial_points[k] = initial_points[i];int b = rng.uniform(0, 255);int g = rng.uniform(0, 255);int r = rng.uniform(0, 255);circle(frame, pts[1][i], 3, Scalar(b, g, r), 3, 8);line(frame, pts[0][i], pts[1][i], Scalar(b, g, r), 3, 8);}}//更新角点vector容量pts[0].resize(k);pts[1].resize(k);initial_points.resize(k);//绘制跟踪线draw_line(frame,pts[0],pts[1]);imshow("frame", frame);char c = waitKey(fps + 10);if (c == 27)break;//更换帧图像,帧角点信息swap(pts[1], pts[0]);swap(old_gray, gray);//在稀疏光源法还要重新初始化,当角点数小于40时,重新初始化if (pts[0].size()<40) {goodFeaturesToTrack(old_gray, feature_pts, 50, 0.01, 50, Mat(), 3, false);pts[0].insert(pts[0].end(), feature_pts.begin(), feature_pts.end());initial_points.insert(initial_points.end(), feature_pts.begin(), feature_pts.end());}}capture.release();
}void QuickDemo::draw_line(Mat& image, vector pts1, vector pts2)
{ vectorlut;RNG rng(12345);for (auto i = 0; i < pts1.size(); ++i) {int b = rng.uniform(0, 255);int g = rng.uniform(0, 255);int r = rng.uniform(0, 255);lut.push_back(Scalar(b, g, r));}for (auto i = 0; i < pts1.size(); ++i) {line(image, pts1[i], pts2[i], Scalar(255, 0, 0), 2, 8);}
}
稠密光流法:
void QuickDemo::dense_shade_flow()
{VideoCapture capture("https://vd4.bdstatic.com/mda-nm67dtz2afxmwat7/sc/cae_h264/1670390212002064886/mda-nm67dtz2afxmwat7.mp4?v_from_s=hkapp-haokan-hbf&auth_key=1670484546-0-0-792e5c9ffc23b54e025e91106b771e99&bcevod_channel=searchbox_feed&cd=0&pd=1&pt=3&logid=3546818474&vid=6396276202448861552&abtest=104960_2&klogid=3546818474");if (!capture.isOpened())cout << "error" << endl;namedWindow("frame", WINDOW_FREERATIO);namedWindow("result", WINDOW_FREERATIO);int fps = capture.get(CAP_PROP_FPS);//定义当前帧,前一帧,并灰度转换Mat frame, preframe;Mat gray, pregray;capture.read(preframe);cvtColor(preframe, pregray, COLOR_BGR2GRAY);Mat hsv = Mat::zeros(preframe.size(), preframe.type());Mat mag = Mat::zeros(hsv.size(), CV_32FC1);Mat ang = Mat::zeros(hsv.size(), CV_32FC1);Mat xpts = Mat::zeros(hsv.size(), CV_32FC1);Mat ypts = Mat::zeros(hsv.size(), CV_32FC1);//输出光流场数据空间定义Mat_ flow;//通道拆分vector mv;split(hsv, mv);Mat bgr;while (true) {bool ret = capture.read(frame);char c = waitKey(fps + 5);if (c == 27)break;cvtColor(frame, gray, COLOR_BGR2GRAY);calcOpticalFlowFarneback(pregray, gray, flow, 0.5, 3, 15, 3, 5, 1.2, 0);for (int row = 0; row < flow.rows; ++row) {for (int col = 0; col < flow.cols; ++col) {const Point2f& flow_xy = flow.at(row, col);//取出对应x、y方向的光流场数据xpts.at(row, col) = flow_xy.x;ypts.at(row, col) = flow_xy.y;}}//转极坐标空间,并归一化到(0,255)cartToPolar(xpts, ypts, mag, ang);ang = ang * 180 / CV_PI/2.0;normalize(mag, mag, 0, 255, NORM_MINMAX);//绝对值处理convertScaleAbs(mag, mag);convertScaleAbs(ang,ang);//各通道图像更新,并融合通道mv[0] = ang;mv[1] = Scalar(255);mv[2] = mag;merge(mv, hsv);cvtColor(hsv, bgr, COLOR_HSV2BGR);imshow("frame", frame);imshow("result", bgr);}capture.release();
}
camshift:
Mat frame, gray; //源图像和源灰度图像
Mat framecopy; //用于拷贝出的源图像
Mat framerect, framerecthsv; //矩形选取后的图像
Rect rect; //鼠标选取的矩形//直方图
int histSize = 200;
float histR[] = { 0,255 };
const float* histRange = histR;
int channels[] = { 0,1 };
Mat dstHist;//保存目标轨迹
std::vector pt;//鼠标控制
bool firstleftbutton = false;
bool leftButtonDownFlag = false; //左键单击后视频暂停播放的标志位
Point rectstartPoint; //矩形框起点
Point rectstopPoint; //矩形框终点
void onMouse(int event, int x, int y, int flags, void* ustc); //鼠标回调函数 void onMouse(int event, int x, int y, int flags, void* ustc)
{//鼠标左键按下if (event == EVENT_LBUTTONDOWN){leftButtonDownFlag = true; //更新按下标志位rectstartPoint = Point(x, y); //设置矩形的开始点rectstopPoint = rectstartPoint; //刚按下时结束点和开始点一样}//当鼠标按下并且开始移动时else if (event == EVENT_MOUSEMOVE && leftButtonDownFlag){framecopy = frame.clone(); //复制源图像rectstopPoint = Point(x, y); //设置矩形的结束点if (rectstartPoint != rectstopPoint){//当矩形的开始点和结束点不同后在复制的图像上绘制矩形rectangle(framecopy, rectstartPoint, rectstopPoint,Scalar(255, 255, 255));}imshow("srcvideo", framecopy);}//当鼠标抬起时else if (event == EVENT_LBUTTONUP){leftButtonDownFlag = false;//按下鼠标标志位复位rect = Rect(rectstartPoint, rectstopPoint);//设置选中后的矩形framerect = frame(rect); //通过矩形获取到选取后的图像imshow("selectimg", framerect);//显示出来选择后的图像cvtColor(framerect, framerecthsv, COLOR_BGR2HSV);//直方图计算calcHist(&framerecthsv, 2, channels, Mat(), dstHist, 1, &histSize, &histRange, true, false);//归一化显示normalize(dstHist, dstHist, 0, 255, NORM_MINMAX);}}
void Quick_Demo::object_follow_demo()
{VideoCapture cap(0);namedWindow("srcvideo", WINDOW_FREERATIO);//设置图像中鼠标事件setMouseCallback("srcvideo", onMouse, 0);bool first = false;while (true){char ch = waitKey(50);//当鼠标左键没有按下时if (!leftButtonDownFlag){cap >> frame;}//图像为空或Esc键按下退出播放 if (ch == 27)break;//如果已经截取了图像进行处理if (rectstartPoint != rectstopPoint && !leftButtonDownFlag){Mat imageHSV;Mat calcBackImage;cvtColor(frame, imageHSV, COLOR_BGR2HSV);//反向投影calcBackProject(&imageHSV, 2, channels,dstHist, calcBackImage, &histRange);TermCriteria criteria(TermCriteria::MAX_ITER +TermCriteria::EPS, 10, 1);CamShift(calcBackImage, rect, criteria);//更新模板Mat imageROI = imageHSV(rect);framerecthsv = imageHSV(rect);calcHist(&imageROI, 2, channels, Mat(),dstHist, 1, &histSize, &histRange);normalize(dstHist, dstHist, 0.0, 1.0, NORM_MINMAX); //归一化 rectangle(frame, rect, Scalar(255, 0, 0), 3); //目标绘制 pt.push_back(Point(rect.x + rect.width / 2,rect.y + rect.height / 2));//储存roi区域的中心点for (int i = 0; i < pt.size() - 1; i++){line(frame, pt[i], pt[i + 1], Scalar(0, 255, 0), 2.5);//绘制roi区域的中心点}}imshow("srcvideo", frame);}cap.release();waitKey(0);destroyAllWindows();
}