What did you do?

In OpenTTD/nml we use pillow to manipulate images, mainly cropping, but I also tested with show() and save().

I think it's related to 2f40926

What did you expect to happen?

I expect the images to be loaded as they were with previous (<8.1.0) pillow versions.

What actually happened?

Depending on the used file it fails to load with OSError: buffer overrun when reading image file or OSError: image file is truncated (0 bytes not processed). But not all images fail to load.

What are your OS, Python and Pillow versions?

• OS: Any (tested on Ubuntu, MacOS and Windows)
• Python: >3.5 (tested on 3.6, 3.7, 3.8)
• Pillow: 8.1.0

This is a simple test case with images that used to load fine. One still works, the two others trigger the different OSError

from PIL import Image

files = ["arctic_railwagons.pcx", "opengfx_generic_trams1.pcx", "opengfx_trains_start.pcx"]

for file in files:
    try:
        with Image.open(file) as im:
            print("{}:{} {} {}".format(file,im.format, im.size, im.mode))
            im.save(file + ".png")
    except OSError as e:
        print("Failed with '{}'".format(str(e)))

Images and test code in pillow-test.zip