`Image.verify` fails to detect corrupted file

[LilithHafner]

I have a .png file that passes verify() but fails on load() I expect the error has to do with compression within the IDAT chunk.

>>> from PIL import Image
>>> img = Image.open("test image (800x600).png")
>>> img.verify()
>>> img = Image.open("test image (800x600).png")
>>> img.load()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/PIL/ImageFile.py", line 274, in load
    raise_oserror(err_code)
  File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/PIL/ImageFile.py", line 67, in raise_oserror
    raise OSError(message + " when reading image file")
OSError: broken data stream when reading image file

Test image:

Versions:

• OS: macOS 12.2.1
• Python: Python 3.9.5
• Pillow: 8.3.0

[radarhere]

It is perhaps worth nothing that if I tell Pillow to accept truncated images, the file loads without a problem.

from PIL import Image, ImageFile
ImageFile.LOAD_TRUNCATED_IMAGES = True
img = Image.open('test image (800x600).png')
img.load()

[radarhere]

The error isn't originating with any check in PngImagePlugin. It is coming from ImageFile.

If you run the code from my previous comment, you will see that the last 16 lines of the image are black. So I don't think that the image is "corrupted" as such. It is only "truncated", ending prematurely.

[radarhere]

https://pillow.readthedocs.io/en/stable/reference/Image.html#PIL.Image.Image.verify

Verifies the contents of a file. For data read from a file, this method attempts to determine if the file is broken, without actually decoding the image data.

I would think that the image data is not broken. @LilithHafner does this answer your question?

[LilithHafner]

I made this .png file by hand with no intention of truncating it. I expect that the reason it is truncated is that I miscalculated one of the checksums. If this is the case, I would say the image data is broken. I'll get back to you if/when I determine the actual reason why this image is not working.

[github-actions]

Closing this issue as no feedback has been received.