This tutorial begins our discussion of how you can blend entire layers in GIMP, starting with changing the opacity of layers, then moving into Layer Modes, which use mathematical functions to allow more complex combinations to achieve certain effects. We discuss the mathematics as a background to more discussion in subsequent tutorials of the specific Layer Modes.

Links:

https://docs.gimp.org/2.10/en/

http://www.thefamousartists.com/

http://www.thefamousartists.com/jeong-seon/geumgang-jeondo

https://www.youtube.com/watch?v=17Iivi0tmug

https://www.youtube.com/watch?v=J9YyQpJa-ns

https://ninedegreesbelow.com/photography/gimp-lch-blend-modes.html

https://en.wikipedia.org/wiki/Blend_modes

https://search.creativecommons.org/

https://search.creativecommons.org/photos/d3067227-9d89-46e6-b5ba-3910432e2a9f

https://search.creativecommons.org/photos/84314932-0a0a-4824-a1a9-fbb3196bfc4c

https://www.ahuka.com/gimp/blending-layers/