Validate self.palette in has_transparency_data()

[gdesmar]

I have a few files that I was able to open and save in Pillow 9.3.0, that result in an error with the newest (10.2.0) version. I believe that the newer has_transparency_data property can cause an error if the palette is not defined from opening a file.

>>> from PIL import __version__, Image
>>> __version__
'10.2.0'
>>> img = Image.open("icon_6.ico")
>>> img.format
'ICO'
>>> img.height
256
>>> img.width
256
>>> img.save("output", format='WEBP')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File ".../python3.12/site-packages/PIL/Image.py", line 2439, in save
    save_handler(self, fp, filename)
  File ".../python3.12/site-packages/PIL/WebPImagePlugin.py", line 338, in _save
    im = im.convert("RGBA" if im.has_transparency_data else "RGB")
                              ^^^^^^^^^^^^^^^^^^^^^^^^
  File ".../python3.12/site-packages/PIL/Image.py", line 1550, in has_transparency_data
    or (self.mode == "P" and self.palette.mode.endswith("A"))
                             ^^^^^^^^^^^^^^^^^
AttributeError: 'NoneType' object has no attribute 'mode'

I believe the solution is as simple as that, but feel free to disregard the PR if it needs a more complex fix.

[radarhere]

There are two ways of looking at this.

• One is that the problem is im.has_transparency_data failing to handle the scenario where im.palette is None.
• The other is that a P mode image shouldn't have a None palette in the first place. P mode images without palettes are really L mode images - see https://pillow.readthedocs.io/en/stable/handbook/concepts.html#modes. This is my inclination.

I had a look through our existing test files, and found this happening with some of our TGA images. I've created #7797 to fix that.

Would you be able to upload the images that are causing this for you?

[gdesmar]

I believe the older version of Pillow was assuming no transparency, but I just tested with VSCode and it looks to think that the icons do have transparency. I would like to point out that I often have to work with corrupted files, so hopefully those won't be too much of a problem.
I added the SHA256 hash for the three icons just in case. Here is the non_palette_icons.zip file.

sha256 hash	name
e2c5c2c687c9f08a77b307da6f4f5dceaee5fb9a2c099adedac977dec8f29211	icon_1.ico
555ca02331d90dcaeaabc66f5e7932e4882916766d4375288c5b8018c7f3a4b0	icon_2.ico
20fde3f789dfeaffcabd1ae1978e6aee10c977cfdc3e8778af6da1e7b794a50b	icon_3.ico

[radarhere]

Thanks. I've created #7798. That should fix your original error.

[gdesmar]

Thank you for your detailed explanations and quick fixes. :)
I will go ahead and close this PR as I doubt it will be useful.

[radarhere]

#7798 has now been merged.