Using enhanced layer features with G'MIC

Karsten Günther takes a look beyond GIMP's standard layer functions. Besides special GIMP operations, tasks provided by G'MIC loom into view.

- Karsten Günther

OUR EXPERT Karsten Günther has written entire books about using GIMP, so four pages is just a morning's work to him.

Both GIMP and the plugin G'MIC have a number of layer functions that - in contrast to those in the article from LXF298 - are neither simple nor obvious. We'll examine them in more detail here. With G'MIC, it usually looks like this: a number of functions available with GIMP can be found with extended possibilities and usually there are a range of additional functions that offer something similar. Some of these functions are rather theoretical, but many are quite practical. The layer-specific functions are mainly found in the Layers, Sequences or Colour sections, and scattered in the Testing section.

Separate colours

GIMP supports the idea of separating colours in layers with the Decompose functions described in the tutorial in LXF298. G'MIC extends these possibilities with the Channels To Layer filter, which enables you to separate channels in layers instead of RGB, CMY and (limited) HSV. However, these functions work somewhat differently from GIMP's own. For example, the RGB layers have to be combined with the Lighten or Screen mode to get a colour-correct image again. For CMY layers, the Difference mode is preset. With HSV splitting, G'MIC creates only two layers: one greyscale layer with the lightenings and one with the colours.

As a result of this colour splitting, there are ways to finely influence the individual layers with the gradation curves (GIMP's Curves tool). Both colour casts and brightness can be edited after. To merge layers created with this G'MIC filter back into one after editing, you must edit the layer stack from below - first the lowest two, then the layer above- with Merge Down.