1. A method of analyzing a first image abstraction and a second image abstraction to determine whether the first image abstraction and the second image abstraction are similar to one another, the method comprising: accessing the first image abstraction; accessing the second image abstraction; combining at least a part of the first image abstraction with at least a part of the second image abstraction to generate a combined image abstraction; and analyzing the combined image abstraction in order to determine whether the first image abstraction and the second image abstraction are similar to one another.