calcOpticalFlowPyrLK causing assertion fail(BUG)

[stevedanomodolor]

My system is ubuntu 20.4 with opencv 4. I am trying to run the euroc example but everytime I get the following error

terminate called after throwing an instance of 'cv::Exception'
  what():  OpenCV(4.2.0) /home/stevedan/libraries/opencv/modules/video/src/lkpyramid.cpp:1257: error: (-215:Assertion failed) maxLevel >= 0 && winSize.width > 2 && winSize.height > 2 in function 'calc'

I was able to trace the problem to the feature tracker file but I don't know how to fix it, any suggestion? in the trackimage function

        else
        {
          std::cout << "**************Here3*****" << std::endl;
          std::cout << prev_img.size() << " " << cur_img.size() << " " << cur_pts.size() <<" " << prev_pts.size() << std::endl;
          cv::calcOpticalFlowPyrLK(prev_img, cur_img, prev_pts, cur_pts, status, err, cv::Size(21, 21), 3);
        }

[stevedanomodolor]

Solves issue, it was something to do with opencv library

[MadlyFX]

How did you wind up solving this?

[stevedanomodolor]

I believe the reason was that I was sending an empty image, make sure that before you send anything that the size is not zero.

[MadlyFX]

Interesting, thanks. I'm trying to use a Realsense D435i and running into this error, but I'm definitely sending valid images.

[stevedanomodolor]

The previus_img size was like empty i think, print the image size as I did else { std::cout << "**Here3*****" << std::endl; std::cout << prev_img.size() << " " << cur_img.size() << " " << cur_pts.size() <<" " << prev_pts.size() << std::endl; cv::calcOpticalFlowPyrLK(prev_img, cur_img, prev_pts, cur_pts, status, err, cv::Size(21, 21), 3); } I think this was the issue, I don't recall exactly