我想简单地加载一个视频文件,将其转换为灰度图像并显示出来。以下是我的代码:
import numpy as np
import cv2
cap = cv2.VideoCapture('cars.mp4')
while(cap.isOpened()):
# Capture frame-by-frame
ret, frame = cap.read()
#print frame.shape
# Our operations on the frame come here
gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
# Display the resulting frame
cv2.imshow('frame',gray)
if cv2.waitKey(1) & 0xFF == ord('q'):
break
# When everything done, release the capture
cap.release()
cv2.destroyAllWindows()
视频一直以灰度播放直到结束,然后窗口卡死并显示“未响应”,终端会出现以下错误信息:
OpenCV Error: Assertion failed (scn == 3 || scn == 4) in cvtColor, file /home/clive/Downloads/OpenCV/opencv-2.4.9/modules/imgproc/src/color.cpp, line 3737
Traceback (most recent call last):
File "cap.py", line 13, in <module>
gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
cv2.error: /home/clive/Downloads/OpenCV/opencv-2.4.9/modules/imgproc/src/color.cpp:3737: error: (-215) scn == 3 || scn == 4 in function cvtColor
我取消注释了print frame.shape语句。它一直打印720,1028,3。但是在视频播放到结尾后,它会冻结一段时间然后关闭并返回。
print frame.shape
AttributeError: 'NoneType' object has no attribute 'shape'
我理解这个断言失败信息通常意味着我试图转换一个空的图片。在使用if(ret):语句开始处理之前,我添加了一个检查空图片的步骤。(还有其他做法吗?)
import numpy as np
import cv2
cap = cv2.VideoCapture('cars.mp4')
while(cap.isOpened()):
# Capture frame-by-frame
ret, frame = cap.read()
#print frame.shape
if(ret): #if cam read is successfull
# Our operations on the frame come here
gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
# Display the resulting frame
cv2.imshow('frame',gray)
if cv2.waitKey(1) & 0xFF == ord('q'):
break
else:
break
# When everything done, release the capture
cap.release()
cv2.destroyAllWindows()
这次视频播放到最后,窗口仍然在几秒钟后冻结并关闭。这次我没有收到任何错误提示。但是为什么窗口会冻结?我该如何修复它?
cap.release()
需要一些时间才能完成。如果你将结尾的两行代码交换,窗口是否仍然冻结? - Arnaud P