检测到运动：

1. 定义关键事件。
2. 将视频剪辑写入包含事件的文件。

• 步骤1： 使用计算机视觉技术检测彩球的存在。
• 步骤＃2： 在视频帧中四处移动时跟踪球，并在移动时绘制其先前位置。

from collections import deque
from imutils.video import VideoStream
import numpy as np
import argparse
import cv2
import imutils
import time
ap = argparse.ArgumentParser()
ap.add_argument("-v", "--video",
	help="path to the (optional) video file")
ap.add_argument("-b", "--buffer", type=int, default=64,
	help="max buffer size")
args = vars(ap.parse_args())

greenLower = (29, 86, 6)
greenUpper = (64, 255, 255)
pts = deque(maxlen=args["buffer"])

if not args.get("video", False):
	vs = VideoStream(src=0).start()

else:
	vs = cv2.VideoCapture(args["video"])

time.sleep(2.0)

while True:

	frame = vs.read()
	# handle the frame from VideoCapture or VideoStream
	frame = frame[1] if args.get("video", False) else frame

	if frame is None:
		break
	frame = imutils.resize(frame, width=600)
	blurred = cv2.GaussianBlur(frame, (11, 11), 0)
	hsv = cv2.cvtColor(blurred, cv2.COLOR_BGR2HSV)
	mask = cv2.inRange(hsv, greenLower, greenUpper)
	mask = cv2.erode(mask, None, iterations=2)
	mask = cv2.dilate(mask, None, iterations=2)
	
	cnts = cv2.findContours(mask.copy(), cv2.RETR_EXTERNAL,
		cv2.CHAIN_APPROX_SIMPLE)
	cnts = imutils.grab_contours(cnts)
	center = None
	if len(cnts) >