There is something manifestly quirky about writing for a digital paint program a filter which emulates painting on canvas. The new media paying homage to the old, perhaps. Certainly, the idea of utility wasn't first and foremost in my mind. It occured to be at some point that I could do it, and that it would be quite straightforward to do. So, without troubling myself too much on whether it would be useful to anyone, I just set out and did it. I suppose working on the companion command line tutorial unleashed many old memories of the days when I painted a bit. This included an instructor whose name I can't remember, though we had spent hours discussing this and that, including the notion: "The physicality of paint."
This filter has a simple remit: transform an image into another that seems like a painting of the image – a finger painting, no less. Not every image relishes to be a finger painting. About half the images I try this filter on turns out dismal results. Those that succeed have simple geometry of bold shapes, and usually bright colors – the kinds of images that one could fingerpaint, if one were actually fingerpainting, and not running software that emulates finger painting.
For the filter dated “26-July-2014” you should find two groups of widgets. The widgets clustered under “Paint Detail” let you furnish hints and policy to guide the business of decomposing an image into strokes; the Physical Paint section in this tutorial covers the underlying mechanisms of these widgets. “Render Detail” allows you to furnish hints about how the paintings should appear. The “Lighting” section in this tutorial furnishes underlying information for that grouping of widgets.
Here are some particulars.
It is worthwhile to activate “Very Verbose” Console or Logfile options on the main Gimp-G'MIC control panel before running the Finger paint filter. These choice spinners are located on the left hand side, under the preview window. The line-by-line G'MIC commentary follows this tutorial fairly closely. There are minor implementation differences between the filter plug in and the walk through script, but nothing that obscures the underlying principles.
For comparision, ambersweet oranges, rendered with fatter fingers than those used in the walkthrough. Finger size for the walk through was about 0.5, here it is about 0.7. We also specified less detail (0.30) and brighter highlights and specular components (0.6 or so).This gives a somewhat more abstract representation. Enjoy the physicality of the paint.