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pythonimageopencvwebcam

Capturing a single frame with Python (using a webcam)

I checked other solutions, but they weren't answering my question. My issue is that whenever I try to capture just one frame from a video (I want to basically take a picture with my webcam) I just get a black window.

Code -

import cv2


cam = cv2.VideoCapture(0)
frame = cam.read()[1]
cv2.imwrite('img2.png', frame)
cv2.imshow("img1", frame)

screenshot - https://i.sstatic.net/oOLCD.jpg

My webcam is USB, 720p at 30fps.

Thanks.

Solution

  • One of two things. It might be that you need to add a waitKey() after cv2.imshow(). Alternatively, you aren't checking the return from the camera for any errors. It could be a connection problem. Here are the two things to do.

    import cv2

cam = cv2.VideoCapture(0)
retval, frame = cam.read()
if retval != True:
    raise ValueError("Can't read frame")

cv2.imwrite('img2.png', frame)
cv2.imshow("img1", frame)
cv2.waitKey()

    The waitKey() function halts the program until a user has entered a key in the window.