Disclosed is a method comprising steps of conducting image preprocessing so as to respectively obtain a candidate object region including a foreground image in a depth map and a color image; determining whether it is necessary to conduct a region growing process with respect to the candidate object region of the depth map; in the former case, conducting the region growing process with respect to the candidate object region of the depth map; and conducting, after the region growing process is conducted with respect to the candidate object region of the depth map, a depth value restoration process with respect to a candidate region.