python控制摄像头拍照_使用Python捕获单个帧(使用网络摄像头)

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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)

My webcam is USB, 720p at 30fps.

Thanks.

解决方案

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.

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