How to use opencv in Python3 to read file from file buffer

Question

I am trying to use this library. In particular these 3 lines:

    image_stream = io.BytesIO(image_bytes)
    frame = cv2.imread(image_stream)

and I am having an exception:

Traceback (most recent call last):
  File "/home/a/Pictures/pycharm-community-2018.3.2/helpers/pydev/pydevd.py", line 1741, in <module>
    main()
  File "/home/a/Pictures/pycharm-community-2018.3.2/helpers/pydev/pydevd.py", line 1735, in main
    globals = debugger.run(setup['file'], None, None, is_module)
  File "/home/a/Pictures/pycharm-community-2018.3.2/helpers/pydev/pydevd.py", line 1135, in run
    pydev_imports.execfile(file, globals, locals)  # execute the script
  File "/home/a/Pictures/pycharm-community-2018.3.2/helpers/pydev/_pydev_imps/_pydev_execfile.py", line 18, in execfile
    exec(compile(contents+"\n", file, 'exec'), glob, loc)
  File "/home/a/Documents/wiker/main.py", line 13, in <module>
    if __name__ == '__main__': main()
  File "/home/a/Documents/wiker/main.py", line 10, in main
    article['video'] = video.make_video_from_article(article)
  File "/home/a/Documents/wiker/video.py", line 15, in make_video_from_article
    frame = cv2.imread(image_stream)
TypeError: bad argument type for built-in operation

But it works on real files. what can be fixed here.

What do you get if you print out print(type(image_stream)) ? — Employee
– Employee, Commented Jan 12, 2019 at 13:59
Possible duplicate of stackoverflow.com/questions/46624449/… — Employee
– Employee, Commented Jan 12, 2019 at 14:10
Read the docs. imread takes a filename as the first parameter, not a stream. It's meant to read from files only. If you want to decode data from memory, you need to use imdecode. — Dan Mašek
– Dan Mašek, Commented Jan 12, 2019 at 14:58

Ulrich Stern · Accepted Answer · 2021-05-28 16:11:08Z

30

Here a solution:

import io, requests, cv2, numpy as np

url = "https://images.pexels.com/photos/236047/pexels-photo-236047.jpeg"
img_stream = io.BytesIO(requests.get(url).content)
img = cv2.imdecode(np.frombuffer(img_stream.read(), np.uint8), 1)

cv2.imshow("img", img)
cv2.waitKey(0)

edited May 28, 2021 at 16:11

answered Jan 12, 2019 at 18:42

Ulrich Stern

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2 Comments

Rami.K Over a year ago

This is awesome thanks - what if I want to do the opposite? go from cv2 to io stream?

ch4rl1e97 Over a year ago

@Rami.K stackoverflow.com/a/64849668/9311137

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