I would like to know how can i paint in normal mode just only on those pixels that are already painted;in this way i can avoid paint outside of the desired area. Is this possible in krita? thanks

Hi Fernando2012,

Very easy!
First you must paint on a transparent layer of course (don't start painting on the white background layer )

If you want to paint only on existing pixels on current canvas you can click on the "Alpha lock" (checkboard icon on the layer stack).

You can also Paint over on a separate layer:
-Create a layer group
-Put the layer with the base shapes in it
-Create another layer on top inside the group, and on this one click the "Alpha disable" (Alpha symbol icon on the layer stack), so it will use layers below as mask.

Have fun!

Hello Animtim, thanks! it works : )