OpenCV 3 Tracker won't work after reinitialization

Question

I have issue using OpenCV 3 tracking module for tracking. It behaves same, either I use interface class (cv::Tracker) or class with implementation (like cv::TrackerMedianFlo

Answer 1

I just ran into the same problem, here's how I got it to work :

tracker->clear();

Ptr<Tracker> trackerNew = Tracker::create( tracker_algorithm );

tracker = trackerNew;
tracker->init( image, boundingBox );

Might not be the right way or the prettiest but it does the job :)

Answer 2

I ran into the same problem and here's my solution: Open the file in opencv_contrib/modules/tracking/src/tracker.cpp and apply the following changes:

-  if( isInit )
+  /*if( isInit )
   {
     return false;
   }
+  */

I recompiled opencv3 and reinstalled it. That fixed it for me. I think they did not want people to reinitialize the tracker for some reason. I am not sure why?

Answer 3

If you want to track a new ROI (region of interest) then I suggest that you should create a new tracker instead of clearing and trying to reuse a previous tracker. Re-use when you need to call init will provide no extra benefit. As you have observed, re-initializing a tracker is not allowed by default.

But if you want to resume tracking of the same object with your correction, it might be possible by doing following steps (I have not tried it myself yet. following code is just a pseudo code)

Ptr<TrackerModel> model = tracker->getModel();
Ptr<TrackerTargetState> lastTargetstate = getLastTargetState();

// Make changes to lastTargetState (update position etc)

// Set lastTargetState, I am not sure if you need to actually set it
// or just editing the object through pointer should work.
model->setLastTargetState(lastTargetstate);