Patent ID: 8761497
Filing Date: 2014-06-24
Classification: G06T

Abstract:
1. A method for detecting and removing shadows, the method comprising the steps of: (i) combining corresponding values from a plurality of frames that are carried by a digital video signal, obtained, directly or indirectly, from a video camera, any two frames of the video signal differing from each other owing to the field of view of the video camera changing by any camera action selected from tilting, panning, zooming or dollying or any combination thereof, said corresponding values being combined so as to create therefrom a background model image of the scene or of a portion thereof, said background model image covering a region greater than a field of view of at least one individual frame of the video signal; (ii) processing the background model image to detect and define within the background model image model shadow zones; (iii) calculating correction factors for some or all of said model shadow zones; (iv) for each of a plurality of frames of the video signal, determining a region of said background model image corresponding to the field of view of the frame, and thereby deriving, in the frame carried by the signal, frame shadow zones that correspond to said model shadow zones; and (v) correcting video signal values within said frame shadow zones.