Python+OpenCV读写视频的方法详解

import cv2 video_capture = cv2.VideoCapture(video_path) while True: flag, frame = video_capture.read() if not flag: break # do something with frame video_capture.release() 

import cv2 video_path = r'D:\peppa\Muddy_Puddles.mp4' video_capture = cv2.VideoCapture(video_path) frame_num = video_capture.get(cv2.CAP_PROP_FRAME_COUNT) # ==> 总帧数 fps = video_capture.get(cv2.CAP_PROP_FPS)               # ==> 帧率 width = video_capture.get(cv2.CAP_PROP_FRAME_WIDTH)     # ==> 视频宽度 height = video_capture.get(cv2.CAP_PROP_FRAME_HEIGHT)   # ==> 视频高度 pos = video_capture.get(cv2.CAP_PROP_POS_FRAMES)        # ==> 句柄位置 video_capture.set(cv2.CAP_PROP_POS_FRAMES, 1000)        # ==> 设置句柄位置 pos = video_capture.get(cv2.CAP_PROP_POS_FRAMES)        # ==> 此时 pos = 1000.0 video_capture.release() 

import cv2 import numpy as np video_path = r'D:\peppa\Muddy_Puddles.mp4' video_capture = cv2.VideoCapture(video_path) cnt = -1 frames1 = [] while True: cnt += 1 flag, frame = video_capture.read() assert flag if 100 <= cnt <200: frames1.append(frame) if cnt>= 200: break video_capture.release() video_capture = cv2.VideoCapture(video_path) frames2 = [] for i in range(100, 200): video_capture.set(cv2.CAP_PROP_POS_FRAMES, i) flag, frame = video_capture.read() assert flag frames2.append(frame) video_capture.release() frames1 = np.array(frames1) frames2 = np.array(frames2) print(np.all(frames1 == frames2))  # ==> check whether frames1 is same as frames2, result is True 

import cv2 import numpy as np import time video_path = r'D:\peppa\Muddy_Puddles.mp4' video_capture = cv2.VideoCapture(video_path) t0 = time.time() while True: flag, frame = video_capture.read() if not flag: break t1 = time.time() video_capture.release() video_capture = cv2.VideoCapture(video_path) t2 = time.time() frame_num = int(video_capture.get(cv2.CAP_PROP_FRAME_COUNT)) for i in range(frame_num): video_capture.set(cv2.CAP_PROP_POS_FRAMES, i) flag, frame = video_capture.read() assert flag t3 = time.time() video_capture.release() print(t1 - t0)  # ==> 76.3 s print(t3 - t2)  # ==> 345.1 s 

# -*- coding: utf-8 -*- import os import cv2 def _extract_frame_mode_1(video_capture, frame_list, root_folder, ext='png'): """ extract video frames and save them to disk. this method will go through all the frames using video_capture.read() Parameters: ----------- video_capture: obtained by cv2.VideoCapture() frame_list: list list of frame numbers root_folder: str root folder to save frames ext: str extension of filename """ frame_list = sorted(frame_list) video_capture.set(cv2.CAP_PROP_POS_FRAMES, 0) cnt = -1 index = 0 while True: cnt += 1 flag, frame = video_capture.read() if not flag: break if cnt == frame_list[index]: filename = os.path.join(root_folder, str(cnt) + '.' + ext) cv2.imwrite(filename, frame) index += 1 def _extract_frame_mode_2(video_capture, frame_list, root_folder, ext='png'): """ extract video frames and save them to disk. this method will use video_capture.set() to locate the frame position and then use video_capture.read() to read Parameters: ----------- video_capture: obtained by cv2.VideoCapture() frame_list: list list of frame numbers root_folder: str root folder to save frames ext: str extension of image filename """ for i in frame_list: video_capture.set(cv2.CAP_PROP_POS_FRAMES, i) flag, frame = video_capture.read() assert flag filename = os.path.join(root_folder, str(i) + '.' + ext) cv2.imwrite(filename, frame) def extract_frame(video_path, increment=None, frame_list=None, mode=1, ext='png'): """ extract video frames and save them to disk. the root folder to save frames is same as video_path (without extension) Parameters: ----------- video_path: str video path increment: int of 'fps' increment of frame indexes frame_list: list list of frame numbers mode: int, 1 or 2 1: go through all the frames using video_capture.read() 2: use video_capture.set() to locate the frame position and then use video_capture.read() to read ext: str extension of image filename """ video_capture = cv2.VideoCapture(video_path) frame_num = int(video_capture.get(cv2.CAP_PROP_FRAME_COUNT)) if increment is None: increment = 1 elif increment == 'fps': fps = video_capture.get(cv2.CAP_PROP_FPS) increment = round(fps) if frame_list is None: frame_list = [i for i in range(0, frame_num, increment)] if frame_num // len(frame_list) > 5 and mode == 1: print("the frames to be extracted is too sparse, " "please consider setting mode = 2 to accelerate") root_folder = os.path.splitext(video_path)[0] os.makedirs(root_folder, exist_ok=True) if mode == 1: _extract_frame_mode_1(video_capture, frame_list, root_folder, ext) elif mode == 2: _extract_frame_mode_2(video_capture, frame_list, root_folder, ext) video_capture.release() if __name__ == '__main__': video_path = r'D:\peppa\Muddy_Puddles.mp4' extract_frame(video_path, increment=30, mode=2) 

video_path = r'D:\peppa\Muddy_Puddles.avi' root_folder = r'D:\peppa\Muddy_Puddles' fourcc = cv2.VideoWriter_fourcc('X', 'V', 'I', 'D') fps = 25 size = (1920, 1080) video_writer = cv2.VideoWriter(video_path, fourcc, fps, size) for i in range(0, 7788, 30): filename = os.path.join(root_folder, str(i) + '.png-600') image = cv2.imread(filename) video_writer.write(image) video_writer.release()