Fix for #653 - animated gifs with mode "P" errors

[benzkji]

@jrief @SmileyChris somehow the FrameAware wrapper did not always preserve the mode.

I was thinking about adding a "THUMBNAIL_PRESERVE_ANIMATIONS = False", so one can easily completly disable animated stuff. Even when not saving the frames, they are currently processed anyway, thus running into potential performance issues.

[benzkji]

@jrief @SmileyChris to be clear, this is an somewhat urgent bugfix, for a regression (see #653 ) that was introduced by my animated formats support PR that was merged for version 2.10. THUMBNAIL_PRESERVE_ANIMATIONS is for later.

[philippemilink]

Can we expect this PR to be merged soon and a release to be published, please?

[benzkji]

Let's see if @SmileyChris or @jrief see this.

[benkonrath]

@benzkji Quick question about this fix: I noticed that the resulting thumbnail is not animated for animated mode P GIFs. You can see this by replacing the last line in the test with this:

            # ...
            thumb = t.get_thumbnail({'size': (500, 50), 'crop': True})
            self.assertTrue(getattr(thumb.image, "is_animated", False))

It looks like to_return = to_return.convert(new_frames[0].mode) removes the animation on the latest version of Pillow (pillow==11.2.1). Is this the expected result?

I've set THUMBNAIL_IMAGE_SAVE_OPTIONS correctly, e.g.:

THUMBNAIL_IMAGE_SAVE_OPTIONS = {
    # ...
    "PNG": {
        "save_all": True,
    },
    "GIF": {
        "save_all": True,
    },
}

I've also tested with animated PNGs and that is working. Any idea?

[benzkji]

@benkonrath yes. It is the workaround. I've not found a way to correctly process the example GIF from this PR, so I thought, better strip animations and have something working. I was not able to spend a lot of time on the problem though, I'm sure there is a solution. But Pillow is sometimes tricky, I must admit.