It's amusing people think it was a photoshop filter. Take a look at the diamonds in the tie. It would take an awesome algo to figure out that this surface is plane covered by diamond-ish things, and straighten it out, rotate it slightly, and enlarge it (while keeping the other constraints of the picture in place) so that the pixel diamonds fit on it well. Not to mention that the pixel diamonds only broadly evoke the of the tie, and are even truncated at the top and bottom in ways calculated to evoke the original, that have nothing to do with mechanical pixelation.

And that's just one tiny element.