pyhthon Opencv截取视频中的图片

import os
import cv2    ##加载OpenCV模块

def video2frames(pathIn='', 
                 pathOut='', 
                 imgname='',
                 only_output_video_info = False, 
                 extract_time_points = None, 
                 initial_extract_time = 0,
                 end_extract_time = None,
                 extract_time_interval = -1, 
                 output_prefix = 'img',
                 
                 jpg_quality = 100,
                 isColor = True):
    '''
    pathIn：视频的路径，比如：F:python_tutorials	est.mp4
    pathOut：设定提取的图片保存在哪个文件夹下，比如：F:python_tutorialsframes1。如果该文件夹不存在，函数将自动创建它
    only_output_video_info：如果为True，只输出视频信息（长度、帧数和帧率），不提取图片
    extract_time_points：提取的时间点，单位为秒，为元组数据，比如，(2, 3, 5)表示只提取视频第2秒， 第3秒，第5秒图片
    initial_extract_time：提取的起始时刻，单位为秒，默认为0（即从视频最开始提取）
    end_extract_time：提取的终止时刻，单位为秒，默认为None（即视频终点）
    extract_time_interval：提取的时间间隔，单位为秒，默认为-1（即输出时间范围内的所有帧）
    output_prefix：图片的前缀名，默认为frame，图片的名称将为frame_000001.jpg、frame_000002.jpg、frame_000003.jpg......
    jpg_quality：设置图片质量，范围为0到100，默认为100（质量最佳）
    isColor：如果为False，输出的将是黑白图片
    '''
    
    cap = cv2.VideoCapture(pathIn)  ##打开视频文件
    n_frames = int(cap.get(cv2.CAP_PROP_FRAME_COUNT))  ##视频的帧数
    fps = cap.get(cv2.CAP_PROP_FPS)  ##视频的帧率
    print(fps)
    dur = n_frames/fps  ##视频的时间
    
    ##如果only_output_video_info=True, 只输出视频信息，不提取图片
    if only_output_video_info:
        print('only output the video information (without extract frames)::::::')
        print("Duration of the video: {} seconds".format(dur))
        print("Number of frames: {}".format(n_frames))
        print("Frames per second (FPS): {}".format(fps)) 
    
    ##提取特定时间点图片
    elif extract_time_points is not None:
        if max(extract_time_points) > dur:   ##判断时间点是否符合要求
            raise NameError('the max time point is larger than the video duration....')
        try:
            os.mkdir(pathOut)
        except OSError:
            pass
        success = True
        count = 0
        while success and count < len(extract_time_points):
            cap.set(cv2.CAP_PROP_POS_MSEC, (1000*extract_time_points[count])) 
            success,image = cap.read()
            if success:
                if not isColor:
                    image = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)  ##转化为黑白图片
                print('Write a new frame: {}, {}th'.format(success, count+1))
                cv2.imwrite(os.path.join(pathOut, "{}_{}.jpg".format(output_prefix, imgname)), image, [int(cv2.IMWRITE_JPEG_QUALITY), jpg_quality])     # save frame as JPEG file
                count = count + 1

    else:
        ##判断起始时间、终止时间参数是否符合要求
        if initial_extract_time > dur:
            raise NameError('initial extract time is larger than the video duration....')
        if end_extract_time is not None:
            if end_extract_time > dur:
                raise NameError('end extract time is larger than the video duration....')
            if initial_extract_time > end_extract_time:
                raise NameError('end extract time is less than the initial extract time....')
        
        ##时间范围内的每帧图片都输出
        if extract_time_interval == -1:
            if initial_extract_time > 0:
                cap.set(cv2.CAP_PROP_POS_MSEC, (1000*initial_extract_time)) 
            try:
                os.mkdir(pathOut)
            except OSError:
                pass
            print('Converting a video into frames......')
            if end_extract_time is not None:
                N = (end_extract_time - initial_extract_time)*fps + 1
                success = True
                count = 0
                while success and count < N:
                    success,image = cap.read()
                    if success:
                        if not isColor:
                            image = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)
                        print('Write a new frame: {}, {}/{}'.format(success, count+1, n_frames))
                        cv2.imwrite(os.path.join(pathOut, "{}_{}.jpg".format(output_prefix, imgname)), image, [int(cv2.IMWRITE_JPEG_QUALITY), jpg_quality])     # save frame as JPEG file
                        count =  count + 1
            else:
                success = True
                count = 0
                while success:
                    success,image = cap.read()
                    if success:
                        if not isColor:
                            image = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)
                        print('Write a new frame: {}, {}/{}'.format(success, count+1, n_frames))
                        cv2.imwrite(os.path.join(pathOut, "{}_{}.jpg".format(output_prefix, imgname)), image, [int(cv2.IMWRITE_JPEG_QUALITY), jpg_quality])     # save frame as JPEG file
                        count =  count + 1

        ##判断提取时间间隔设置是否符合要求    
        elif extract_time_interval > 0 and extract_time_interval < 1/fps:
            raise NameError('extract_time_interval is less than the frame time interval....')
        elif extract_time_interval > (n_frames/fps):
            raise NameError('extract_time_interval is larger than the duration of the video....')
        
        ##时间范围内每隔一段时间输出一张图片
        else:
            try:
                os.mkdir(pathOut)
            except OSError:
                pass
            print('Converting a video into frames......')
            if end_extract_time is not None:
                N = (end_extract_time - initial_extract_time)/extract_time_interval + 1
                success = True
                count = 0
                while success and count < N:
                    cap.set(cv2.CAP_PROP_POS_MSEC, (1000*initial_extract_time+count*1000*extract_time_interval)) 
                    success,image = cap.read()
                    if success:
                        if not isColor:
                            image = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)
                        print('Write a new frame: {},{}th'.format(success, count+1))
                        cv2.imwrite(os.path.join(pathOut, "{}_{}.jpg".format(output_prefix,imgname)), image, [int(cv2.IMWRITE_JPEG_QUALITY), jpg_quality])     # save frame as JPEG file
                        count = count + 1
            else:
                success = True
                count = 0
                while success:
                    cap.set(cv2.CAP_PROP_POS_MSEC, (1000*initial_extract_time+count*1000*extract_time_interval)) 
                    success,image = cap.read()
                    if success:
                        if not isColor:
                            image = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)
                        print('Write a new frame: {}, {}th'.format(success, count+1))
                        cv2.imwrite(os.path.join(pathOut, "{}_{}.jpg".format(output_prefix, imgname)), image, [int(cv2.IMWRITE_JPEG_QUALITY), jpg_quality])     # save frame as JPEG file
                        count = count + 1


if __name__ == "__main__":
    pathIn = 'C:/Users/Administrator/www/video_back/video_back/upload/1.mp4'
    pathOut = 'C:/Users/Administrator/www/video_back/video_back/upload/'
    imgname = 'dog'
    video2frames(pathIn,pathOut,imgname,extract_time_points=(1,))