tkinter camera threads

[Yoriz]

You will only get a return of -1 when it first travels through the function and the following evaluates to true

if(not cap.isOpened() ):
        return -1

otherwise, it travels right through the function and will return None.
Directly calling the GUI from inside another thread will cause problems.
Depending on how fast it travels through the function and starts another thread looping back on itself, it might be overwhelming the GUI with changes.