Failure to identify PNG image

[Kelketek]

What did you do?

Attempted to read a PNG image file usable by most applications

What did you expect to happen?

Pillow reads and processed the PNG.

What actually happened?

PIL.UnidentifiedImageError: cannot identify image file <_io.BufferedReader name='example.png'>

What are your OS, Python and Pillow versions?

• OS: Ubuntu 22.04.5 LTS
• Python: 3.11.1
• Pillow: 11.0.01

--------------------------------------------------------------------
Pillow 11.0.0
Python 3.11.1 (main, Jan 31 2023, 09:47:18) [GCC 11.3.0]
--------------------------------------------------------------------
Python executable is /home/fox/.pyenv/versions/artconomy/bin/python3
Environment Python files loaded from /home/fox/.pyenv/versions/artconomy
System Python files loaded from /home/fox/.pyenv/versions/3.11.1
--------------------------------------------------------------------
Python Pillow modules loaded from /home/fox/.pyenv/versions/artconomy/lib/python3.11/site-packages/PIL
Binary Pillow modules loaded from /home/fox/.pyenv/versions/artconomy/lib/python3.11/site-packages/PIL
--------------------------------------------------------------------
--- PIL CORE support ok, compiled for 11.0.0
--- TKINTER support ok, loaded 8.6
--- FREETYPE2 support ok, loaded 2.13.2
--- LITTLECMS2 support ok, loaded 2.16
--- WEBP support ok, loaded 1.4.0
--- JPEG support ok, compiled for libjpeg-turbo 3.0.4
--- OPENJPEG (JPEG2000) support ok, loaded 2.5.2
--- ZLIB (PNG/ZIP) support ok, loaded 1.2.11
--- LIBTIFF support ok, loaded 4.6.0
--- RAQM (Bidirectional Text) support ok, loaded 0.10.1, fribidi 1.0.8, harfbuzz 10.0.1
*** LIBIMAGEQUANT (Quantization method) support not installed
--- XCB (X protocol) support ok
--------------------------------------------------------------------

from PIL import Image
from io import BytesIO

with open('example.png', 'rb') as image_file:
    Image.open(image_file)

File here:

[radarhere]

If I run pngcheck example.png, I get

example.png  CRC error in chunk pHYs (computed d2dd7efc, expected 679fd252)
ERROR: example.png

So there is a problem with your image.

If you would like to ignore the problem, you can do so with LOAD_TRUNCATED_IMAGES.

from PIL import Image, ImageFile
from io import BytesIO

ImageFile.LOAD_TRUNCATED_IMAGES = True

with open('example.png', 'rb') as image_file:
    Image.open(image_file)

[Kelketek]

Thanks, @radarhere . The site I'm working on here allows general uploads by the public-- is there any security implication to allowing LOAD_TRUNCATED_IMAGES or is this only a check on internal consistency?

Are there any other concerns I should be aware of?

[radarhere]

#6843 (comment)

a truncated image is an image that is truncated, e,g, #3023. For PNGs, the definition of this is broadened to include images that have missing chunk data or invalid chunk checksums.

[Kelketek]

Got it. Thanks, @radarhere . Just to make sure, this is still a valid issue in your view, right? Any error with actually processing the image should happen upon loading, but identification shouldn't fail here?

[radarhere]

That idea has been suggested before in #1687

My conclusion was

I don't think our formats allow for this.

• FpxImagePlugin initially _accepts an image, but may later decide it's not FPX after all. So if an error occurs before that second line, it shouldn't be marked as identified. I don't see how you could communicate that distinction purely by catching errors without further obscuring the original cause.
• ImtImagePlugin does not have a good ability to distinguish between a malformed file and a file of another type.

It could have been a good idea if we were starting Pillow from scratch, but for a library concerned with backwards compatibility, I don't think it can be achieved without rewrites that seem excessive.

[Kelketek]

@radarhere In that case, should this issue be closed or is there anything to be done here?

[radarhere]

I don't think there is anything further, no.

We've even documented this scenario to try and help further - https://pillow.readthedocs.io/en/stable/PIL.html#PIL.UnidentifiedImageError