Can't upload screenshot, "isn't actually an image"

[Desour]

Summary

I'm trying to upload screenshots as jpg, by converting them from png with ffmeg. But contentdb fails to recognize them as image.

Steps to reproduce

• Take some png image. (For example: default_lava.png from devtest)
• Convert it to jpg with ffmpeg: ffmpeg -i input_file output_file
• Try uploading it as a screenshot on contentdb.
• It fails with the message: Uploaded image isn't actually an image

Here's an example, it's clearly a jpeg image, just ask file:

And it is, in fact, an image. Stop gaslighting me!

Relevant code, probably

https://github.com/minetest/contentdb/blob/master/app/logic/uploads.py

[SmallJoker]

https://docs.python.org/3/library/imghdr.html

imghdr is deprecated. Maybe filetype is a viable alternative.

[rubenwardy]

If I open it in GIMP and re-export it again, it works. So something is odd with the encoding that imghdr can't recognise

[sfan5]

CDB already depends on Pillow, I'm sure it can determine the image type.