Question

代码读取train1.mov文件，显示cv2.imshow('res', res)也保存名为output.avi的文件。问题是，output.avi大约是40 kb并且是空的。但cv2.imshow('res', res)显示整个视频。然后显示以下错误。

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;这就是为什么你的imshow一直在工作但它出错并且没有完成写while循环后发生的视频的原因。

cap.read()返回的第一个值是关于帧是否存在/被读取的布尔值。因此，您只需在代码中插入if-else块即可在读取帧时执行处理，如果没有，则quit while循环，以便您可以完成帧的编写。

这应该修补你的代码：

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。

无法在Python中使用OpenCV打开已保存的视频（Windows 10）

1 个答案: