OpenCV Error: (-215)size.width>0 && size.height>0 in function imshow

Question

I am trying to make a face tracker that combines Haar Cascade Classification with Lucas Kanade good feature detection. However, I keep getting an error that I cannot figure

Answer 1

That error also shows when the video has played fine and the script will finish but that error always throws because the imshow() will get empty frames after all frames have been consumed.

That is especially the case if you are playing a short (few sec) video file and you don't notice that the video actually played on the background (behind your code editor) and after that the script ends with that error.