DestroyWindow does not close window on Mac using Python and OpenCV

Question

My program generates a series of windows using the following code:

def display(img, name, fun):
    global clicked

    cv.NamedWindow(name, 1)
    cv.ShowIm         


        

Answer 1

Sayem2603

I tried your solution and it worked for me - thanks! I did some trial and error and discovered that looping 4 times did the trick for me... or posting the same code 4 times just the same..

Further, I drilled down to:

cv2.destroyAllWindows()
cv2.waitKey(1)
cv2.waitKey(1)
cv2.waitKey(1)
cv2.waitKey(1)

or simply calling DestroyAllWindows and then looping the waitKey() code 4 times:

cv2.destroyAllWindows()
for i in range (1,5):
    cv2.waitKey(1)

Worked as well. I am not savvy enough to know why this works exactly, though I assume it has something to do with the interruption and delay created by looping that code(?)

Matthäus Brandl said, above, that the third waitKey() worked for him, so perhaps it is slightly different on each system? (I am running Linux Mint with 3.16.1 kernel and python 2.7)

The delay, alone, doesn't explain it, as simply increasing the delay time on the waitKey() does not do the trick. (Also looped print("Hello") 1000 times instead of using wiatKey() just to see if the delay that created helped any - it did not.) Must have something more to do with how waitKey() interacts with window events.

OpenCV Docs say: "This function is the only method in HighGUI that can fetch and handle events, so it needs to be called periodically for normal event processing unless HighGUI is used within an environment that takes care of event processing."

Perhaps it creates an interrupt of sorts in the GUI display that allows the destroyAllWindows() action to process?

J