I have eventually produced a plug-in that others might find useful!
It creates three masked layers of different saturations, high, medium, and low. These allow largely independent adjustment of the saturation of the three layers.
I have frozen the undo stack to speed-up the operation and reduce memory usage.
It would be good to be able to undo the script with a "ctrl-z" and merge the layers with a key-press on completion, but this is way beyond my capability!
The only slight problem - when I run the script from the terminal, I get the error message "EEEEeEeek! 1 GeglBuffers leaked". I don't know if this is significant and I have been unable to find the source of the error.
Any comments, criticism, and advice are most welcome.
Attachment:
saturation_h_m_l.zip [2.54 KiB]
Downloaded 54 times
Attachment:
saturation_h_m_l_tut.zip [51.15 KiB]
Downloaded 70 times
Edit: The files have been updated to allow them to work with other languages. 29/10/2021.
Edit: Updated to latest version of plug-in - corrected error in script.
Edit: File updated to version 4 with options to select transition between masked layers.