A good way to reproduce a cartoon-like tone?

I made a paint software using SkiaSharp.
https://github.com/satochibi/UgomemoPro
Unlike other software, it reproduces cartoon-like tones.
As we use "SetPixel" of "SKBitmap" extensively,
Every time you need to repaint (when changing the window size / when undoing), the process becomes very heavy.
This method does not seem to be suitable for repainting in the first place.
Is there another way to handle it faster?