Shadow detection using a physical basis

Shadow detection is an important aspect of foreground/background classification. Many techniques exist, most of them assuming that casting a shadow results only in a change in intensity and no change in color. In this paper we show that in most practical indoor and outdoor situations there will also be a color shift. We propose an algorithm for estimating this color shift from the images, and using it to remove shadow pixels. The proposed algorithm is compared experimentally to an existing algorithm using real image sequences. Results show a significant improvement of performance.