BMP Image File treated as invalid

[jerzyk]

when assigning a .bmp (windows bitmap) image to an ImageField field, django reports error, responsible line, that raises an error is django/forms/fields.py:695 (to_python)

f.content_type = Image.MIME[image.format]

file is validated properly (opened, validated) and at the and, it's mime_type is detected by using a dictionary Image.MIME.

This dictionary is not documented and does not contain entries for BMP file, so it may be assumed that Django is using it's private api.

There are two options - push on Pillow to make this public API and fix an issue or use different method to find mime-type (e.g. python's standard mimetypes library)

[Tim Graham]

It's a regression in 1.8 (#10935), so qualifies for a backport. At least we could ​catch the exception and set f.content_type = None in that case.

[Andriy Sokolovskiy]

​https://github.com/django/django/pull/4869

I think setting content_type to None will be enough.

[Tim Graham <timograham@…>]

In cf6ce279:

Fixed #24948 -- Fixed crash when uploading bitmap images in forms.ImageField

[Tim Graham <timograham@…>]

In 8abe2d0:

[1.8.x] Fixed #24948 -- Fixed crash when uploading bitmap images in forms.ImageField

Backport of cf6ce279c7671a4c83c960c5c526f92679a4fac8 from master