1. Method for enabling replacement of a current representation of a target in each image of a sequence of successive video images of a scene delivered by a video camera, with a stored pattern, independent of the size of the target representation, said method comprising the steps of: (a) storing data identifying said target as set of a plurality of distributed characterizing points and a full representation of said target; (b) automatically recognizing at least a subset of said set of characterizing points in each current image in turn in the sequence and deriving an estimated location, size and perspective of the current representation of said target in said current image from the relative locations of the characterizing points in said current image; (c) geometrically transforming said full representation of said target responsive to said estimated size and perspective; (d) determining, by pixel-by-pixel comparison, which part of the geometrically transformed representation of the target is identical to a part of the current representation of said target as it appears in said current image; and (e) generating data necessary for enabling replacement of each said current representation of the target by a matching representation of said stored pattern as a result of the transformation and comparison.