截取视频 opencv python

# coding: utf-8
import cv2 as cv
import os
print('===============================================================')
print('本工具有4个功能，键入不同数字，执行不同功能：1，2，3，4')
print('如果输入有误，程序报错或执行结果（无结果）')
print('\n')
print('输入数字1：截取视频全部帧')
print('输入数字2：自定义区间取帧')
print('输入数字3：自定义间隔数取帧')
print('输入数字4：自定义取某一帧')
print('\n')
print('===============================================================')
all = eval(input('请键入1-4中的对应数字数字（ 选择相应的功能 ）：'))
if (all ==1):
	filepath = './input'          
	pathDir = os.listdir(filepath)  
	for allDir in pathDir:          
		Frame = 0  
		c = 1  
		videopath = r'./input/'+allDir  
		vc = cv.VideoCapture(videopath) 
		path = './Video_Result（All）Frame/'
		if not os.path.exists(path):   
			os.mkdir(path)
		if vc.isOpened(): 
			rval , frame = vc.read()
		else:
			rval = False
		timeF = 1                    
		while rval:
			rval,frame = vc.read()     
			if rval==False:
				break
			if(c%timeF==0):	
				#frame = frame[0:1070,200:1840]
				cv.imencode('.jpg',frame)[1].tofile(path +'/' + str(Frame) +'-'+ allDir[:-4] + '.jpg')    
				print('正在截取第' + str(Frame) + "帧，请稍后……")
				Frame += 1
	print('\n','处理完成，请移步------→ ：Video_Result（All）Frame查看结果')
if (all ==2):
# coding: utf-8
	filepath = './input'          
	pathDir = os.listdir(filepath)
	print('\n')
	a = eval(input('请输入待截取的开始帧：'))
	b = eval(input('请输入待截取的结束帧：'))	  
	for allDir in pathDir:          
		Frame = 0  
		c = 1  
		videopath = r'./input/'+allDir  
		vc = cv.VideoCapture(videopath) 
		path = './Video_Result（自定义区间）Frame/'
		if not os.path.exists(path):   
			os.mkdir(path)
		if vc.isOpened(): 
			rval , frame = vc.read()
		else:
			rval = False
		timeF = 1                    
		while rval:
			rval,frame = vc.read()     
			if rval==False:
				break
			if(c%timeF==0):	
				#frame = frame[0:1070,200:1840]						
				if (Frame >= a and Frame <=b ): # 50--80帧的数据
					cv.imencode('.jpg',frame)[1].tofile(path +'/' + str(Frame) +'-'+ allDir[:-4] + '.jpg')    
					print('正在截取第' + str(Frame) + "帧，请稍后……")   
				Frame += 1      
	print('\n','处理完成，请移步------→ ：Video_Result（自定义区间）Frame查看结果')
# coding: utf-8
if (all ==3):
	filepath = './input'            
	pathDir = os.listdir(filepath) 
	print('\n')
	interval = eval(input('请输入需要间隔帧数：'))
	for allDir in pathDir:       
		a = 1 
		c = 1  
		videopath = r'./input/'+allDir  
		vc = cv.VideoCapture(videopath) 
		path = './Video_Result（Interval）Frame/'
		if not os.path.exists(path):   
			os.mkdir(path)
		if vc.isOpened(): 
			rval , frame = vc.read()
		else:
			rval = False
		timeF = interval                      
		while rval:
			rval,frame = vc.read()      
			if rval==False:
				break
			if(c%timeF==0):
				cv.imencode('.jpg',frame)[1].tofile(path +'/' + str(a) +'-'+ allDir[:-4] + '.jpg')    
				print('正在截取第' + str(a) + "帧，请稍后……")
			a += 1
			c += 1
			cv.waitKey(1)
		vc.release()
	print('\n','处理完成，请移步------→ ：Video_Result（Interval）Frame查看结果')
if (all ==4):
# coding: utf-8
	filepath = './input'            
	pathDir = os.listdir(filepath) 
	print('\n')
	only_one = eval(input('请输入需要截取的特定一帧：'))
	for allDir in pathDir:          
		a = only_one
		videopath = r'./input/'+allDir  
		vc = cv.VideoCapture(videopath) 
		path = './Video_Result（Only-1）Frame/'
		if not os.path.exists(path):    
			os.mkdir(path)
		if vc.isOpened(): 
			rval , frame = vc.read()
		else:
			rval = False
		while rval:
			vc.set(cv.CAP_PROP_POS_FRAMES, a)
			rval,frame = vc.read()     
			cv.imencode('.jpg',frame)[1].tofile(path +'/' + str(a) +'-'+ allDir[:-4] + '.jpg')  
			print(str(a) +'-'+ allDir[:-4] + '---视频截取完成')
			break
	print('\n','处理完成，请移步------→ ：Video_Result（Only-1）Frame查看结果')