“Painty” is a software application that I've been developing since 2007; it's currently up to version 3-point-something. The software uses programmable nodes in a GUI which allow the operator (me) to diagram the image processing and painting stages.
Painty's color processing aims to replace the source image's photographic color palette with a painter's palette — shadows are filled with color, white's are opaque and colors are translucent. All shape analysis and brush strokes are calculated by the computer; there is no manual painting.
The final painting stage is implemented in OpenGL and can output images at 8k resolution in about a minute.
All the images below were painted from copyright-free NASA photos.