Hilbert Mapping

This is drawn by walking a Hilbert curve through the 256x256x256 colour cube, visiting all 16,777,216 colours in order, and walking a second Hilbert curve through the square, visiting all 16,777,216 pixels in order. Both walks are the same length, so the nth colour goes to the nth pixel. A Hilbert curve keeps nearby points nearby, so colours that sit close together in the cube land close together in the image.