1. A system for background image subtraction, the system comprising: a computing device having a processor and memory, the processor programmed to receive video data, via a 3D application programming interface (API), from a camera, the video data containing (i) at least one colored image of one or more subjects and (ii) corresponding depth information; the processor further programmed to: assign pixels of the video data to one of three different regions including foreground (FG), background (BG), and unclear (UC); re-assign UC pixels to FG or BG using a function that considers (i) color and background history (BGH) information associated with the UC pixels and (ii) color and BGH information associated with pixels near the UC pixels; and construct at least one new image by overlaying the FG regions on top of a new background.