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import java.util.ArrayList;
import java.util.Random;
import org.opencv.core.*;
import org.opencv.highgui.HighGui;
import org.opencv.imgproc.Imgproc;
import org.opencv.video.Video;
import org.opencv.videoio.VideoCapture;
class OptFlow {
public void run(String[] args) {
String filename = args[0];
VideoCapture capture = new VideoCapture(filename);
if (!capture.isOpened()) {
System.out.println("Unable to open this file");
System.exit(-1);
}
// Create some random colors
Scalar[] colors = new Scalar[100];
Random rng = new Random();
for (int i = 0 ; i < 100 ; i++) {
int r = rng.nextInt(256);
int g = rng.nextInt(256);
int b = rng.nextInt(256);
colors[i] = new Scalar(r, g, b);
}
Mat old_frame = new Mat() , old_gray = new Mat();
// Since the function Imgproc.goodFeaturesToTrack requires MatofPoint
// therefore first p0MatofPoint is passed to the function and then converted to MatOfPoint2f
MatOfPoint p0MatofPoint = new MatOfPoint();
capture.read(old_frame);
Imgproc.cvtColor(old_frame, old_gray, Imgproc.COLOR_BGR2GRAY);
Imgproc.goodFeaturesToTrack(old_gray, p0MatofPoint,100,0.3,7, new Mat(),7,false,0.04);
MatOfPoint2f p0 = new MatOfPoint2f(p0MatofPoint.toArray()) , p1 = new MatOfPoint2f();
// Create a mask image for drawing purposes
Mat mask = Mat.zeros(old_frame.size(), old_frame.type());
while (true) {
Mat frame = new Mat(), frame_gray = new Mat();
capture.read(frame);
if (frame.empty()) {
break;
}
Imgproc.cvtColor(frame, frame_gray, Imgproc.COLOR_BGR2GRAY);
// calculate optical flow
MatOfByte status = new MatOfByte();
MatOfFloat err = new MatOfFloat();
TermCriteria criteria = new TermCriteria(TermCriteria.COUNT + TermCriteria.EPS,10,0.03);
Video.calcOpticalFlowPyrLK(old_gray, frame_gray, p0, p1, status, err, new Size(15,15),2, criteria);
byte StatusArr[] = status.toArray();
Point p0Arr[] = p0.toArray();
Point p1Arr[] = p1.toArray();
ArrayList<Point> good_new = new ArrayList<>();
for (int i = 0; i<StatusArr.length ; i++ ) {
if (StatusArr[i] == 1) {
good_new.add(p1Arr[i]);
Imgproc.line(mask, p1Arr[i], p0Arr[i], colors[i],2);
Imgproc.circle(frame, p1Arr[i],5, colors[i],-1);
}
}
Mat img = new Mat();
Core.add(frame, mask, img);
HighGui.imshow("Frame", img);
int keyboard = HighGui.waitKey(30);
if (keyboard == 'q' || keyboard == 27) {
break;
}
// Now update the previous frame and previous points
old_gray = frame_gray.clone();
Point[] good_new_arr = new Point[good_new.size()];
good_new_arr = good_new.toArray(good_new_arr);
p0 = new MatOfPoint2f(good_new_arr);
}
System.exit(0);
}
}
public class OpticalFlowDemo {
public static void main(String[] args) {
System.loadLibrary(Core.NATIVE_LIBRARY_NAME);
new OptFlow().run(args);
}
}
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