Painting with DEGAS: (digitally extrapolated graphics via algorithmic strokes)

Abstract

Most photograph-to-oil-painting algorithms are based off of the techniques described by [Litwinowicz 1997] and improved upon by [Hertzmann 2001]. They are essentially fully-automated processes which place strokes at random, choosing stroke orientations to follow local gradient normals. These strokes are built up over several layers, each layer in a decreasing order of stroke size - painting broad strokes and then filling in details. Outside of the initial chosen parameters and some masking considerations, the user has little agency in how the algorithm chooses stroke placement, nor has the ability to make direct changes or touch-ups until every stroke is laid down on the canvas - essentially it behaves like an "image filter" applied as one would adjust contrast or add texture.