python - 无法在 Python (Windows 10) 中使用 OpenCV 打开保存的视频

Question

代码读取 train1.mov 文件，显示 cv2.imshow('res', res) 同时保存一个名为 output.avi。问题是，output.avi 大约 40 kb 并且是空的。但是 cv2.imshow('res', res) 显示了整个视频。然后显示如下错误。

Python 代码:

import numpy as np
import cv2

cap = cv2.VideoCapture('C:\\Users\\khan1\\Desktop\\python project\\color_threshold\\train1.mov')

fourcc = cv2.VideoWriter_fourcc(*'XVID')
out = cv2.VideoWriter('C:\\Users\\khan1\\Desktop\\python project\\color_threshold\\output.avi',fourcc, 20.0, (640,480))

while(cap.isOpened()):
    _, frame = cap.read()

    hsv = cv2.cvtColor(frame, cv2.COLOR_BGR2HSV)
    lower_green = np.array([40, 60, 60]) 
    upper_green = np.array([80, 255, 255])

    mask = cv2.inRange(hsv, lower_green, upper_green)
    mask = cv2.GaussianBlur(mask, (7, 7), 0)
    res = cv2.bitwise_and(frame, frame, mask=mask)

    out.write(res)

    cv2.namedWindow("res", cv2.WINDOW_NORMAL)
    cv2.imshow('res', res)
    if (cv2.waitKey(1) & 0xFF) == ord('q'): # Hit `q` to exit
         break

# Release everything if job is finished
out.release()
cap.release()
cv2.destroyAllWindows()

错误:

OpenCV Error: Assertion failed ((scn == 3 || scn == 4) && (depth == CV_8U || depth == CV_32F)) in cv::cvtColor, file C:\build\master_winpack-bindings-win32-vc14-static\opencv\modules\imgproc\src\color.cpp, line 9815
Traceback (most recent call last):
  File "C:/Users/khan1/Desktop/python project/color_threshold/savevid.py", line 19, in <module>
    hsv = cv2.cvtColor(frame, cv2.COLOR_BGR2HSV)
cv2.error: C:\build\master_winpack-bindings-win32-vc14-static\opencv\modules\imgproc\src\color.cpp:9815: error: (-215) (scn == 3 || scn == 4) && (depth == CV_8U || depth == CV_32F) in function cv::cvtColor


Process finished with exit code 1

我该如何解决？

Answer 1

很明显你的错误发生在最后一帧；这就是为什么您的 imshow 一直在工作，但它出错并且没有完成编写 while 循环之后发生的视频。

cap.read() 返回的第一个值是一个 bool 值，表示帧是否存在/是否被读取。所以你可以简单地在你的代码中插入一个 if-else block 来在帧被读取时执行你的处理，并且 quit while 循环如果不，这样你就可以写完框架了。

这应该修补您的代码:

import numpy as np
import cv2

cap = cv2.VideoCapture('C:\\Users\\khan1\\Desktop\\python project\\color_threshold\\train1.mov')

fourcc = cv2.VideoWriter_fourcc(*'XVID')
out = cv2.VideoWriter('C:\\Users\\khan1\\Desktop\\python project\\color_threshold\\output.avi',fourcc, 20.0, (640,480))

while(cap.isOpened()):
    ret, frame = cap.read()
    if ret:

        hsv = cv2.cvtColor(frame, cv2.COLOR_BGR2HSV)
        lower_green = np.array([40, 60, 60]) 
        upper_green = np.array([80, 255, 255])

        mask = cv2.inRange(hsv, lower_green, upper_green)
        mask = cv2.GaussianBlur(mask, (7, 7), 0)
        res = cv2.bitwise_and(frame, frame, mask=mask)

        out.write(res)

        cv2.namedWindow("res", cv2.WINDOW_NORMAL)
        cv2.imshow('res', res)
        if (cv2.waitKey(1) & 0xFF) == ord('q'): # Hit `q` to exit
            break
    else:
        break

# Release everything if job is finished
out.release()
cap.release()
cv2.destroyAllWindows()

查看同一过程的示例 here .