cv2.imwrite returning false instead of saving image

Question

I am working on a code to save an image. Instead of saving image cv2.imwrite function is returning false. I have reproduced the problem in the below code:

Uni_ID = 123
cam=cv2.VideoCapture(0)
rett, img = cam.read()

now = datetime.now()
dtString =  now.strftime('%d-%m-%Y')
timeString = now.strftime('%H:%M:%S')
path = 'IMG'
name = path + '/' + dtString
#     print(name)
if not os.path.exists(name):
    os.makedirs(name)
imgName = name + '/'+ str(Uni_ID) + '_' + timeString + '.jpg'
print(imgName)
cv2.imwrite(imgName, img)

Instead of saving image, the cv2.imwrite function on the last line is returning false. The output of the code is :

IMG/03-09-2020/123_17:59:58.jpg
False

I guess you are using windows, that's why you get the problem since filenames with ':' are not considered. Instead you can use / or -, just change the now.strftime('%H-%M-%S') — JenilDave
– JenilDave, Commented Sep 3, 2020 at 14:00

jupiterbjy · Accepted Answer · 2020-09-03 13:55:03Z

5

You can't use : in file name.

>>> cv2.imwrite(r'123_17:59:58.jpg', np.array(i))
False
>>> cv2.imwrite(r'123_17_59_58.jpg', np.array(i))
True

If you're not sure whether a filename would be valid or not - try opening it first.

>>> f = open(r'123_17:59:58.jpg', 'wt')
Traceback (most recent call last):
  File "<input>", line 1, in <module>
OSError: [Errno 22] Invalid argument: '123_17:59:58.jpg'

>>> f = open(r'123_17_59_58.jpg', 'wt')
>>>

edited Sep 3, 2020 at 13:55

answered Sep 3, 2020 at 13:51

jupiterbjy

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7 Comments

Adam Boinet Over a year ago

Nope, cv2.imwrite(r'123_17:59:58.jpg', np.array(i)) is a perfectly valid command

jupiterbjy Over a year ago

Not in windows.

Adam Boinet Over a year ago

Ok, I didn't know that (I'm on Linux, it worked fine for me). But I think the true issue here are the slashes in the name

jupiterbjy Over a year ago

I agree on that. TBH I think cv2 need to raise error instead of returning False. That's not pythonic -

rajan Over a year ago

Agree that cv2 should throw more descriptive error. This same behavior in my case was caused by something totally different - the file name being too long.

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