The anti aliasing quality of the pen and brush is low

[Charltsing]

this is PhotoDemon

checked or unchecked

RenderTarget.SetAntialiasMode(D2D1_ANTIALIAS_MODE_PER_PRIMITIVE) ??

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this is use C# gdi in my program

[tannerhelland]

Thank you for filing this issue, @Charltsing . I apologize that it has taken me so long to reply. (I have spent the past month working on a new pipeline for PhotoDemon stable releases, so it won't take me so long to ship stable release in the future!)

PhotoDemon's Pencil tool also uses GDI+. I can double-check the tool settings to ensure I am using the best GDI+ settings for this purpose.

The Pen tool uses a custom brush mask, because it has to manually "dab" each stroke depending on brush settings. The mask generation code is simple, but I am investigating switching to a third-party brush library in the future (perhaps the mypaint brush library).

PhotoDemon needs a better brush engine, and hopefully I can address the antialiasing behavior as part of a broader brush update.

[Charltsing]

https://github.com/liole/PicturesqueEditor

I guess your problem may lie in the brush code. If you have time, you can take a look at this