Win11 24H2 .NET bug rendering text to image using GDI+

[tracktownsoftware]

Description

Previous to 24H2, running the same code to generate an image with text produced an identical image every time that passed a pixel-by-pixel comparison test. As of 24H2 the same images generated twice fail pixel-by-pixel comparison.

This is a .NET issue. The tests pass when I use .NET Framework 4.8.

Note: I reported this bug to Windows 11 feedback before realizing this is a .NET issue (https://aka.ms/AAuckmw).

Reproduction Steps

Repo with code to reproduce the bug: https://github.com/tracktownsoftware/Win11-24H2-ImageTextBug
Press the "Compare Images" button.

Expected behavior

Expected behavior:

• The code generates identical images every time.
• Pixel-by-pixel comparison passes (before Windows 11 version 24H2)

Actual behavior

Actual behavior:
The same images are generated twice but fail pixel-by-pixel comparison. This started with the release of Windows 11 version 24H2.

Note: On a computer with 24H2 I changed the test app to use .NET Framework 4.8. The comparison tests passed, showing this to be a .NET issue.

Regression?

Yes this is a regression. If you run the repo test app with a Win11 version before 24H2 then it works.

Known Workarounds

Don't upgrade to Windows 11 to 24H2

Configuration

No response

Other information

No response

[ViktorHofer]

@JeremyKuhne

[JeremyKuhne]

@tracktownsoftware Fwiw, we use the same GDI+ APIs on .NET Framework as we do in .NET.

@Olina-Zhang can you see if you can reproduce the behavior and validate that it only happens on .NET and not .NET Framework?

[tracktownsoftware]

@JeremyKuhne @Olina-Zhang
Thank you for looking at this. Let me know if there is anything else I can do, like adding a DN48 version of the test project to the Win11-24H2-ImageTextBug repo.

[Olina-Zhang]

@Olina-Zhang can you see if you can reproduce the behavior and validate that it only happens on .NET and not .NET Framework?

We can use physical machine see the .NET and .NET framework have different results on Win11 24H2, not VMs

[tracktownsoftware]

Setting up a Hyper-V VM with the older 23H2 shows the NET8 test working.

After updating the 23H2 Hyper-V VM to 24H2, this test now fails.

edited to crop images