12-06-2012, 02:18 PM
Since it's always 4x4 pixel boxes (it's most noticable in the backgrounds there) I'd suppose that comes from some block compression similar to what DirectX does (they compress 4x4 pixel blocks by reducing them to two colours and two interpolated colours in between, then they have tiny indices for each pixel telling which one of the four colours they have). Though I guess you'd know more about what they do in this game as you made the extraction tool.