Texture Synthesis
I was working on a post about this approach to texture synthesis when ExUtumno posted this video and saved me the trouble of trying to describe it. Based on P. F. Harrison’s PhD dissertation, the algorithm fills in pixels in a random order, using a best-fit search to find close matches from the example source texture. This turns out to work particularly well for synthesizing pixel art.
ExUtumno has been working on texture synthesis for a while now, in part for eventual use in the in-development RPG, ITER IN IGNOTUM. Some of the previous code is on GitHub, in the SynTex repository.
I think it’s an excellent example of how new artistic tools can empower artists and let them create more art. There’s a version of this algorithm available in a plugin for GIMP if you’d like to try playing with it yourself.