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samples/cpp/tutorial_code/video/meanshift/meanshift.cpp

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+#include <iostream>
+#include <opencv2/imgcodecs.hpp>
+#include <opencv2/imgproc.hpp>
+#include <opencv2/videoio.hpp>
+#include <opencv2/highgui.hpp>
+#include <opencv2/video.hpp>
+
+using namespace cv;
+using namespace std;
+
+int main(int argc, char **argv)
+{
+    const string about =
+        "This sample demonstrates the meanshift algorithm.\n"
+        "The example file can be downloaded from:\n"
+        "  https://www.bogotobogo.com/python/OpenCV_Python/images/mean_shift_tracking/slow_traffic_small.mp4";
+    const string keys =
+        "{ h help |      | print this help message }"
+        "{ @image |<none>| path to image file }";
+    CommandLineParser parser(argc, argv, keys);
+    parser.about(about);
+    if (parser.has("help"))
+    {
+        parser.printMessage();
+        return 0;
+    }
+    string filename = parser.get<string>("@image");
+    if (!parser.check())
+    {
+        parser.printErrors();
+        return 0;
+    }
+
+    VideoCapture capture(filename);
+    if (!capture.isOpened()){
+        //error in opening the video input
+        cerr << "Unable to open file!" << endl;
+        return 0;
+    }
+
+    Mat frame, roi, hsv_roi, mask;
+    // take first frame of the video
+    capture >> frame;
+
+    // setup initial location of window
+    Rect track_window(300, 200, 100, 50); // simply hardcoded the values
+
+    // set up the ROI for tracking
+    roi = frame(track_window);
+    cvtColor(roi, hsv_roi, COLOR_BGR2HSV);
+    inRange(hsv_roi, Scalar(0, 60, 32), Scalar(180, 255, 255), mask);
+
+    float range_[] = {0, 180};
+    const float* range[] = {range_};
+    Mat roi_hist;
+    int histSize[] = {180};
+    int channels[] = {0};
+    calcHist(&hsv_roi, 1, channels, mask, roi_hist, 1, histSize, range);
+    normalize(roi_hist, roi_hist, 0, 255, NORM_MINMAX);
+
+    // Setup the termination criteria, either 10 iteration or move by atleast 1 pt
+    TermCriteria term_crit(TermCriteria::EPS | TermCriteria::COUNT, 10, 1);
+
+    while(true){
+        Mat hsv, dst;
+        capture >> frame;
+        if (frame.empty())
+            break;
+        cvtColor(frame, hsv, COLOR_BGR2HSV);
+        calcBackProject(&hsv, 1, channels, roi_hist, dst, range);
+
+        // apply meanshift to get the new location
+        meanShift(dst, track_window, term_crit);
+
+        // Draw it on image
+        rectangle(frame, track_window, 255, 2);
+        imshow("img2", frame);
+
+        int keyboard = waitKey(30);
+        if (keyboard == 'q' || keyboard == 27)
+            break;
+    }
+}