(07-03-2023, 08:11 PM)fluffypanda Wrote: changes mountains to brighter colors and sand to darker
Maybe you're searching for something like below?
GIMP top menu go to:
Colors > Invert
Then for the map
Filters > Generic > Distance Map...,
Adjust to your liking, there are many options. (Try Edge handling > Above threshold for the sea to not look like mountains as it's at the edge)
Perhaps a bit of Filters > Blur > Gaussian Blur... after creating the map to smooth things out depending your needs.