Grid vs. arbitrary placement of files for generating animated photomosaics

A traditional photomosaic is a still image where a larger picture is created by selectively arranging small picture tiles on a blank, gridded canvas. We show interesting and engaging animations can be generated from an evolutionary search for the final photomosaic image. We then investigate two different tile placement strategies for generating the animations. In the first strategy tiles can only be placed in fixed cells in a 2 dimensional grid and it is not possible for tiles to overlap. This strategy is implemented with a genetic algorithm. In the second strategy, which is implemented using genetic programming, the tiles can be placed in any position and at an arbitrary rotation. It is possible for one tile to be placed on top of another so a method for dealing with overlap is needed. We have investigated three methods for dealing with overlap. The second strategy generates more engaging animations but at considerably increased computational cost. We conclude that evolutionary search can be used to produce very engaging animations in which a target image gradually emerges from an initial random collection of tiles.