look breaking change in 0.26

[MrLixm]

Hello,
I have found that when running the exact same script using rawpy==0.25.1 and rawpy==0.26.0 I get different pixel data.

This can be reproduced with different raw files from different camera brands so it's not linked to the file used.
correction in post below

I am on Windows 10 and haven't tested other platforms.

script to reproduce

from rawpy import __version__
import rawpy._rawpy as rawpy

print(__version__)

SRC_PATH = r"...\P1001570.dng"

raw_file = rawpy.RawPy()
raw_file.open_file(SRC_PATH)
try:
    image_array = raw_file.postprocess()
finally:
    raw_file.close()

print(image_array[0][0])

results

• with rawpy 0.26.0 installed

0.26.0
[97 25 48]

• with rawpy 0.25.1 installed

0.25.1
[63  4  1]

---

I have not yet look at what is causing this issue.
However I can't help but think it's weird how when suddenly AI slop is introduced on the project (mention of Copilot in release note) there instantly a hard-breaking bug. Or maybe this is just an unfortunate coincidence and I'm exaggerating.
Still this is a very cool project and I thank you a lot for maintaining it but please don't add AI slop to it.

Thanks,
Liam.

[MrLixm]

Correction: this seems to be partially related to the file format,
I have mostly DNGs that were all bugged, I also tested a .RAF (bugged), however the ARW was working fine between both versions of rawpy.

[letmaik]

Duplicate of #283. Thanks for reporting this. Please check the PR that introduced the issue: #278. The behaviour of libraw is highly surprising here, adding a 0 correction value to the black level is apparently different than leaving out the offset, the API docs of libraw are also underspecified ("Per-channel corrections to user_black."). It might even be a bug on their side. The real issue why this slipped through, with or without using AI, is that this project is missing test cases that sanity check the postprocess output visually and I didn't run a visual check myself. I will add such tests soon.

[letmaik]

@MrLixm Could you please download the preview wheel of the next version from here and test it? https://github.com/letmaik/rawpy/actions/runs/21816882046?pr=285

[MrLixm]

tested the windows python-3.10 wheel and it seems to be working, thanks !