Preserve RGBA image.mode

[z4r]

No description provided.

[grantmcconnaughey]

Merged! Thank you.

[vonmaster]

Hi,

This pull request is causing an issue OSError: cannot write mode RGBA as JPEG, when uploading a PNG with a RGBA mode. I suggest to revert to the previous state:

if image.mode != "RGB":
    image = image.convert("RGB")

Detail Error Log:

>>> from django.utils import six
>>> thumb = six.BytesIO()
>>> image.save(thumb, settings.AVATAR_THUMB_FORMAT, quality=quality)
Traceback (most recent call last):
  File "/opt/python/run/venv/local/lib64/python3.6/site-packages/PIL/JpegImagePlugin.py", line 611, in _save
    rawmode = RAWMODE[im.mode]
KeyError: 'RGBA'

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/usr/lib64/python3.6/code.py", line 91, in runcode
    exec(code, self.locals)
  File "<console>", line 1, in <module>
  File "/opt/python/run/venv/local/lib64/python3.6/site-packages/PIL/Image.py", line 2151, in save
    save_handler(self, fp, filename)
  File "/opt/python/run/venv/local/lib64/python3.6/site-packages/PIL/JpegImagePlugin.py", line 613, in _save
    raise OSError(f"cannot write mode {im.mode} as JPEG") from e
OSError: cannot write mode RGBA as JPEG
>>> image.mode
'RGBA'
>>> image.mode not in ("RGB", "RGBA")