Why getbbox() returns None?

[drunkwcodes]

What did you do?

I tried to use the following code to chop the image edges, but the getbbox() keeps returning None.

What did you expect to happen?

I tried 9.5.0 and 8.4.0, it all returns None, but it worked and returned a tuple in older version which I can't tell.

What are your OS, Python and Pillow versions?

• OS: Windows 10
• Python: 3.10.11
• Pillow: 9.5.0

from PIL import Image, ImageChops


im1 = Image.open("001-0.png")
im = im1.convert(mode="RGBA")
im1.close()
bg = Image.new(im.mode, im.size, im.getpixel((0, 0)))
diff = ImageChops.difference(im, bg)
diff = ImageChops.add(diff, diff, 2.0, -100)


bbox = diff.getbbox()

assert bbox is not None

[Yay295]

Because diff is fully transparent.

https://pillow.readthedocs.io/en/stable/releasenotes/7.1.0.html#if-present-only-use-alpha-channel-for-bounding-box

For images with an alpha channel, only the alpha channel is used when calculating the bounding box.

[nulano]

You may be interested in #4849 / #7123.

[drunkwcodes]

Thanks for your help. I will use RGB mode instead now and look forward to the PR being merged.