Script-Fu Charcoal-Layer-FX v1.0 by Micomicon March 2011
A Gimp script which takes the effect from my Charcoal script and adds it as a layer or layers. NB. Does not require charcoal.scm to be installed.
Opening the Layers Dialog and scrolling through the layer modes afterwards can produce some interesting results akin to adding a watercolour wash, the strength of which can be varied by adjusting the opacity slider.
Thanks to mahvin for this change of direction.
To install (Linux):
Download and move the script file charcoal-layer-FX.scm to /yourhome/.gimp-2.x/scripts.
Charcoal-Layer-FX will be available the next time you start the Gimp and can be found in the menu IMAGE / FILTERS / ARTISTIC.
Works on any RGB or grayscale image but note that adding chalk will fail if applied to a layer which does not contain any image or contains an image with too limited a tonal range ie. "Add chalk highlights" won't work if there is nothing to make the chalk highlights from.