Random Spread from Center

Each pixel is colored depending on the order of activation in the random spread algorithm.

The algorithm assigns one of 3 states to pixels: deactivated, border and activated.

Starts at the middle (2048,2048), where the pixel is set to border.

Every iteration, one randomly chosen border pixel become activated, then sets its deactivated neighbors to border. Repeat until all pixels are activated.

(Uses "Suave" post mapping)