参考:https://cloud.tencent.com/developer/article/1711584
cap = cv2.VideoCapture(0, cv2.CAP_DSHOW)
cap.set(cv2.CAP_PROP_FOURCC, cv2.VideoWriter_fourcc('M', 'J', 'P', 'G'))
ret, frame = cap.read()
cv2.imshow("capture",frame)
shell = win32com.client.Dispatch("WScript.Shell")
shell.SendKeys('%')
win32gui.SetForegroundWindow(win32gui.FindWindow(None,"capture"))
win32gui.ShowWindow(win32gui.FindWindow(None,"capture"), win32con.SW_SHOW)