1. A method for preprocessing an image of a vehicle interior to remove a portion of the image corresponding to a seat back comprising: generating a contour image from the image; selecting one of a plurality of contour models that most closely matches the generated contour image, a given contour model being associated with one of a plurality of possible seat positions; determining a plane of separation between a seat back and a seat occupant within the image based on the selected contour model; and removing a portion of the image corresponding to the seat back based on the determined plane of separation to isolate an image of the seat occupant.