Patent ID: 8498477

Claim:
A computer-implemented method for image matching, the method comprising: capturing, by the computer, a digital image of an item; determining, by the computer, an image index for the digital image, the image index being invariant to a first symmetrical geometric transformation, but variant to a second symmetrical geometric transformation, by the computer performing at least steps (i)-(iv): (i) subdividing the digital image into at least four image regions; (ii) identifying a plurality of region groups, each including a symmetric pair of the image regions such that a combined color distribution of the symmetric pair of image regions is invariant to the first symmetrical geometric transformation, but variant to the second symmetrical geometric transformation; (iii) determining a plurality of combined color histograms corresponding respectively to the plurality of region groups; and (iv) determining the image index according to at least the plurality of combined color histograms; and selecting, by the computer, from an inventory of previously captured item images, a plurality of previously captured item images having image indices similar to the determined image index, the selected plurality of previously captured item images being possible matches for the digital image without respect to the first symmetrical geometric transformation, but with respect to the second symmetrical geometric transformation.