Goodle was made in Godot as a fun test to see if it was possible. It currently has most basic features required for basic pixel painting, but with time it will have way more improvements and features ;)
it can be tested here (I try to update it often so check the releases or if you have Godot 3.1.1-stable then you can load the Project Files)
https://github.com/Mainman002/Goodle