working with png graphics creates unwanted colors

[Drachenbauer]

Hello

I like to create exact pixelarts for my self coded games.
I use 4-8 special choosen colors to build my graphics from to make them resemble a classic old videogame style.
So i sometimes use the indexed mode to check the used palette of my graphic.
For edition my graphics i only use pencil, color-fill and copy/paste selections.
But in the late time i noticed, that often extra colors appear, thar are just slightly different from one of my choosen colors.
How can this happen?

[Ofnuts]

If your images are color indexed it cannot happen. If they are not, many things can make these color appear: selection and paint tools that use anti-aliasing, transforms with an interpolation other than None...

[Drachenbauer]

(12-04-2022, 08:43 PM)Ofnuts Wrote: If your images are color indexed it cannot happen. If they are not, many things can make these color appear: selection and paint tools that use anti-aliasing, transforms with an interpolation other than None...

I thaught, the pencil tool always replaces affected pixels exavtly with the choosen color.
And for the fill tool "smooth edges" is deactivated.

[Ofnuts]

Can you attach one of the affected PNG (<500KB) and the source XCF (< 2MB)?