错误信息：
[ WARN:0] global /tmp/pip-req-build-sw_3pm_8/opencv/modules/videoio/src/cap_v4l.cpp (1004) tryIoctl VIDEOIO(V4L2:/dev/video0): select() timeout.
Traceback (most recent call last):
  File "main.py", line 26, in <module>
    cv2.imshow("image", frame)
cv2.error: OpenCV(4.4.0) /tmp/pip-req-build-sw_3pm_8/opencv/modules/highgui/src/window.cpp:376: error: (-215:Assertion failed) size.width>0 && size.height>0 in function 'imshow'

错误原因：未设置视频流格式

添加：cap.set(cv2.CAP_PROP_FOURCC, cv2.VideoWriter.fourcc('M', 'J', 'P', 'G'))  # 视频流格式

说明：具体还得根据摄像头决定