Nearest-Neighbor Flood Fill

The circle is filled using a flood fill algorithm that walks along the inside border of the circle, filling each pixel with the nearest neighbor to the average of the already-filled in pixels. The circle border is generated by stepping through the Hue-Sorted RGB space for each octant. The outside of the circle is filled using a flood-fill based off of a randomly added to stack. I implemented the nearest neighbor search using an oct-tree.