1. A method to identify items depicted in an input image, the method comprising: comparing, with a processor, a first image signature associated with the input image with a plurality of reference signatures associated with a plurality of reference images to identify a first reference image matching the input image; identifying, with the processor, a first group of items depicted in the input image as corresponding to a first group of reference items registered with the first reference image; determining, with the processor, a first region of the input image that differs from a corresponding first region of the first reference image; and processing, with the processor, the first region of the input image based on a template to identify a second item depicted in the input image.