Algorithm 1 Shadow-based Tracking Algorithm

Require: A background image, current color image, and the skeleton data of Hf. Ensure: The position of the occluded person Hb. 1: Search the region R including the shadow in the current color image according to the value of   a that was computed in the initialization stage, and the skeleton data of Hf; 2: Extract Hb’s shadow in R; 3: Compute the position of Hb based on the shadow; 4: Return position of Hb