I read somewhere and I thought it was here about a plugin/script that was used to remove repeating patterns or frequencies from an image. Sorta like a fourier but for any type of pattern and not just moire.

If it was here, I can't seem to find the right keywords to track it down. If it wasn't here, maybe someone could offer some advice on how to remove what I would call "banding" I guess from an image. (If even possible.)

You are looking for this plugin I believe that uses FFT. G'MIC can do this too by the way.

http://registry.gimp.org/node/24411

Thanks but I have that and the FFT in G'MIC, but the one I was seeking had nothing to do with FFT if I remember correctly.

Fourier filters have no effect on banding that I can find.

Is it like Selective Gaussian Blur?

No, it must be something I saw somewhere else then if you don't know. I got the impression it was a fairly new plugin, but now I wonder if I was just dreaming.

From what I remember it somehow found repeating distortion patterns in an image like Fourier does with moire, but was more flexible. I don't remember however why I didn't bookmark or save the plugin right then and there so i could try it. There is also the possibility I just misunderstood what I read I guess.
Anyway, if I figure it out, I'll post here.

I am still open to any idea on how to save an image like this. I run into this banding problem quite often and would love to be able to use some of these images.

Just tried Iain's Denoise under G'MIC>Repair and it does a pretty good job at removing the bands but you loose details in the dark areas. I tried blur set to color and then the merged result ran bilateral filter (G'MIC) with good results too but still loose a lot of details

Thanks for the tips, will try them out.