Export to PNG on half-size gives noise artifacts

[gewoonm]

I've exported the attached document to a half-size PNG using the menu-option (not the export-persona). As you can see in the attached PNG there is a square of noise in the bottom-left corner.

I've exported this same file (with some minor edits) in the same way yesterday, and the square of noise was in a different part.

Am I doing something wrong, or is this a bug?

puzzle4.afphoto

[gewoonm]

I should maybe add some context to this thing

I make a cryptographic puzzle for friends and family each Easter. I've started on the puzzle for 2023 already, it takes me a year to finish all images (18 in total).

The theme this year is "Sugary treats", for example candy or milkshake. Any guesses what the solution is for the image above?

[Lee D]

Can you open the apps Preferences > Performance and see if Hardware Acceleration (Windows) or Metal Compute (macOS) is enabled? If so please disable and restart the app and try exporting again as I'm not seeing any corruption after exporting. 

[gewoonm]

@Lee D, I've included three versions now:

- default settings (Metal Compute on): the square of noise is now in a different location as yesterday

- disabled Metal Compute: the "square block of noise" is gone, but new artifacts over the whole image have come back in return

- a screenshot of the image how it looks when zoomed out to approximately the same size: this looks as I would expect the exports look

Also added a screenshot of the settings screen. I have version 1.10.5 of the Affinity Photo (not Designer, I picked the wrong forum to post this in, perhaps you can move this thread to the correct forum?).

[Lee D]

Viewing the file on my Mac at 100% within Affinity Photo and also viewing the export at the same view level doesn't show any issues, the the attached screenshot. Open the apps Preferences > Performance again and try changing the Display setting to OpenGL.

 

[gewoonm]

Hi @Lee D, please note that I'm exporting at 50%. I've done as you asked, set it to OpenGL and the image still has the artifacts.

I've also now exported to 100% with OpenGL (resulting in no artifacts) and then resized to 50% in Apple Preview and this also results in no artifacts. So it is possible to resize this image to 540 in PNG without introducing artifacts.

[gewoonm]

hi @Lee D, is there anything I can do to give you more information to find the problem here?

[Lee D]

Not sure at the moment, when ever we encounter rendering issues, turning off Hardware/Metal Acceleration usually resolves the issue on the systems that experience it. Below is you file open in Photo on my system (Metal Compute enabled) showing the export settings and the exported file open in Apple Preview.

You can try setting the renderer to Software to see the results. Alo make sure macOS is fully up to date as any graphics or any other drivers are part of the upgrade process.

[gewoonm]

Very strange this... I've tried the same image on a much older machine, and there the export works okay (same Affinity Photo version, but Catalina 10.15.7 on a 2012 machine).