1. A method to identify image versions, the method comprising: determining, with a processor, whether a difference between a block of pixels of a first image represented by a first signature and a block of pixels of a reference image represented by a second signature matching the first signature is resolvable using a transformation operation; in response to determining the difference is unresolvable using the transformation operation, including the block of pixels of the first image in a difference region of the first image; generating, with the processor, a third signature different from the difference region of the first image to represent the difference region of the first image; and storing the third signature with version information associated with first image.