The algorithm that creates this thing is:

For each complex number c calculate the following: For all gaussian integers g like 1+1i, 2+2i, 3+3i... when calculating g/c which percentage results in a gaussian integer again? The higher the percentage, the lighter the pixel.

UPDATE 24.10.2012:

This post created a lot of response on Hacker News (and sparked a very interesting discussion), Twitter and various other websites as well as on the discussion section below. It was visited 30,000 times on the first day alone. Many very intelligent comments where made. Here are some reflections and updates: