How to edit saturation levels in gimp
Some times you need to edit the saturation of an image with more fine-grained control than just a slider, for example to keep saturated colors, but remove a tint from the grey table below.
This is our initial picture:
First step is to decompose the image to HSV by going to Colors > Components > Decompose and choosing HSV from the drop-down.
I wanted to desaturate only the parts of the image that already have low saturation, so that the mobile phone, graphics card and cable stay nice and vibrant. I used the following curve on the saturation layer that I got from the decomposition to black out all areas that don't have high saturation.
I inverted the image, and applied it as mask to the initial one getting this:
I duplicated the initial layer and deleted the mask from the duplicate so that the saturated parts show through the transparent areas of our masked layer.
Any changes I do to the masked layer now will aply only to the unmasked parts, leaving the high saturation parts of the image unchanged. This is the finished work: