python opencv waitKey(1) not responding to input on Mac

Question

I'm very new to opencv, and I've been trying to get user input to exit out of all my open windows and escape the while loop. I've tried a bunch of different conditions, and checked that my Mac is giving keyboard permissions to python, but for some reason the waitKey function doesn't seem to be registering when I input anything into the keyboard. Any suggestions on what I should do ?

while True:
    screenshot = py.screenshot()
    screenshot = np.array(screenshot)
    screenshot = cv.cvtColor(screenshot, cv.COLOR_BGR2RGB)

    cv.imshow('Computer Vision', screenshot)

    if cv.waitKey(1) == ord('q'):
        print("shit")
        cv.destroyAllWindows()
        break

Does the window that OpenCV creates have focus when you're pressing the key? — Dan Mašek
– Dan Mašek, Commented Jun 18, 2021 at 15:51
yeah it does, but it doesn't seem to update even when its selected and im pressing a key. — Hank Helmers
– Hank Helmers, Commented Jun 18, 2021 at 15:54
OK. edit the question and add the version of OpenCV that this is occurring with, and make your example a proper minimal reproducible example to allow others that use Mac to easily reproduce it. — Dan Mašek
– Dan Mašek, Commented Jun 18, 2021 at 18:09

mhudnell · Accepted Answer · 2021-06-18 16:17:32Z

1

Try cv2.waitKey(1) & 0xFF == ord('q'): as 0xFF can be necessary on certain OSs.

You may also try inspecting the values of cv.waitKey(1) and ord('q') to see how they differ.

edited Jun 18, 2021 at 16:17

answered Jun 18, 2021 at 15:24

mhudnell

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9 Comments

Hank Helmers Over a year ago

im trying to get a constant screenshots displayed, and when I use waitKey(0) it won't continuously show me the screenshots, just a singular one

mhudnell Over a year ago

Apologies, i see. Perhaps try if cv2.waitKey(1) & 0xFF == ord('q'):. It appears 0xFF can be necessary on certain OSs. Refer to stackoverflow.com/questions/53357877/usage-of-ordq-and-0xff

mhudnell Over a year ago

You may also try inspecting the values of cv.waitKey(1) and ord('q') to see how they differ.

Hank Helmers Over a year ago

right, so I tried the & 0xFF thing didn't seem to make a difference, and then the values of waitKey and ord('q), are -1 and 113 respectively. I just can't get the wait key to return any value other than -1

Christoph Rackwitz Over a year ago

it returns -1 upon timeout (1 means 1 millisecond of timeout). call waitKey(10000) so you have 10 seconds to press a key.

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