I am trying to create a node in Blender that would allow me to do what you would do with an audio equalizer but on the spatial frequencies of an image: A sort of panel with eight controllers, from low to high spatial frequencies, which allows me to attenuate or increase a certain frequency plus a second panel that allows me to increase the contrast on each of the eight frequencies.
The idea came to me after playing a bit with Materialize, a well-known open-source software that serves to generate textures from a photograph and is used a lot in the world of video games. To generate a height map (but also other maps) it offered a panel with various controllers that allowed to act on the frequency.
On the Internet I have found practically nothing that is not the separation of frequencies made in Photoshop to correct skin imperfections. This procedure divides an image into low and high frequencies and then reassembles them. My problem is: How do I split an image into several different spatial frequencies (not just two) and then reassemble them to get the original image again but with the possibility of modulating them individually. Now, regardless of the software, what mathematical operations could I use fr this?
I'm doing tests with Blender nodes. The node is a group of other nodes, I'm not using Python.