The docs are here:
– https://gmic.eu/reference.shtml
– https://raw.githubusercontent.com/dtschump/gmic/master/src/gmic_stdlib.gmic
– gmic-community/template.gmic at master · dtschump/gmic-community · GitHub
I haven’t delved into Natron yet. In G’MIC channels are spectrum channels (e.g. red) and layers are images (e.g. image_name[index]).
If you are using the GUI plugin, there is a selection menu for inputs. You can select the following:
Screenshot from plugin launched from GIMP.
