解决OpenCV读完视频报错的问题

最近由于项目的需要，经常需要使用opencv读视频操作，会经常遇到一个问题，就是视频读完之后会出现报错的情况，虽然不影响代码结果，但是对于吹毛求疵的我实在忍受不了。

会报错的程序：

# -*-coding:utf-8-*-
"""
File Name: read_video.py
Program IDE: PyCharm
Create File By Author: Hong
"""
import cv2
 
 
def read_video(video_path: str):
    """
    OpenCV读视频小工具，解决视频读完报错的问题
    :param video_path: 输入需要读取的视频文件路径
    :return: 没有返回值
    """
    print('视频路径：', video_path)
    cap = cv2.VideoCapture(video_path)
    while cap.isOpened():
        # get a frame
        ret, frame = cap.read()
 
        cv2.imshow("capture", frame)
 
        if cv2.waitKey(1) & 0xFF == ord('q'):
            break
    print('视频读完！')
    cap.release()
    cv2.destroyAllWindows()
 
 
if __name__ == '__main__':
    path = r'D:\multi_insect_videos\multi_object00.mp4'
    read_video(path)

这个程序可以把视频正常读完，但是结束之后会输出错误。

Traceback (most recent call last):
  File "E:/PyCharmDocument/create_ST_image/multi_insect_processing/crop_video_to_images.py", line 76, in <module>
    read_video(path)
  File "E:/PyCharmDocument/create_ST_image/multi_insect_processing/crop_video_to_images.py", line 65, in read_video
    cv2.imshow("capture", frame)
cv2.error: OpenCV(4.5.3) C:\Users\runneradmin\AppData\Local\Temp\pip-req-build-uzca7qz1\opencv\modules\imgproc\src\color.cpp:182: error: (-215:Assertion failed) !_src.empty() in function 'cv::cvtColor'

原因是视频结束后，opencv的imshow()函数获取不到帧就出错了。解决方法：在imshow()之前加入判断，只有当有帧时才读，没有帧时直接退出循环。

不会报错的代码:

# -*-coding:utf-8-*-
"""
File Name: read_video.py
Program IDE: PyCharm
Create File By Author: Hong
"""
import cv2
 
 
def read_video(video_path: str):
    """
    OpenCV读视频小工具，解决视频读完报错的问题
    :param video_path: 输入需要读取的视频文件路径
    :return: 没有返回值
    """
    print('视频路径：', video_path)
    cap = cv2.VideoCapture(video_path)
    while cap.isOpened():
        # get a frame
        ret, frame = cap.read()
        if not ret:
            break
        cv2.imshow("capture", frame)
 
        if cv2.waitKey(1) & 0xFF == ord('q'):
            break
    print('视频读完！')
    cap.release()
    cv2.destroyAllWindows()
 
 
if __name__ == '__main__':
    path = r'D:\multi_insect_videos\multi_object00.mp4'
    read_video(path)

程序输出结果：

视频路径： D:\multi_insect_videos\multi_object00.mp4
视频读完！
 
Process finished with exit code 0

更多Python小工具请参考GitHub仓库: https://github.com/YouthJourney/python-script-tools