“Flood fill” refers to multiple variants of an algorithm (wikipedia: flood fill) for changing the color of pixels within contiguous area of like-colored existing pixel colors. Think paint bucket tool in Photoshop. In early computer graphics, the efficiency of operations that changed a few hundred pixel values was the paramount concern, and although a conceptually trivial procedural problem, flood fill algorithms bring elegance to the fore of discourse. However, that elegance is hidden within the process. How can that elegance itself manifest as image? Under normal circumstances, once the fill is complete, the algorithm is irrelevant, but if the algorithm is purposefully modified with a flaw the paradigm shifts from problem solving to artistic invention.

The tactics used to flaw the flood in this image involve, first, the irregular stepping from pixel to pixel. This allows the fill to cross over boundaries, and when coupled with a gradually changing fill color, patterns emerge that are dependent on, but distinct in geometry from, the bounds.

The flood fill algorithm and multiple flawing tactics are documents and further explored in the Computational Drawing Book.