Patent ID: 7327888

Claim:
A method of pattern matching for recognition of objects within an image using a model defined by a set of one or more model primitives representative of large scale structures of an archetype, the method comprising steps of: deriving at least one target primitive representative of a large scale structure of the image: for each target primitive: identifying any model primitives that at least partially match the target primitive, and for each identified model primitive, calculating a geometric figure of merit indicative of a degree of geometric correspondence between the target primitive and the model primitive; and accumulating the geometric figures of merit; wherein the step of deriving at least one target primitive comprises steps of: detecting geometric features within the image; analyzing the detected geometric features to find large scale structures of the image; approximating each large scale structure with at least one respective primitive; deriving a basis from at least one of the primitives; and representing each of the primitives as invariants in the derived basis; wherein the step of deriving a basis comprises the steps of calculating an origin of a respective local coordinate system and calculating an orientation of the respective local coordinate system; wherein the step of deriving a basis further comprises the steps of deriving a plurality of bases and selecting at least one of the plurality of derived bases; and wherein the step of selecting at least one of the plurality of derived bases comprises any one or more of: selecting bases derived using relatively large primitives; selecting at most two bases derived using any one primitive; selecting bases having respective origins distributed substantially evenly across the image; and selecting bases in respect of which the orientation of the respective coordinate system is parallel to at least one primitive used in the derivation of the respective basis.