1. An image processing apparatus comprising: a region determiner configured to receive image data and perform a region determination by determining whether each of a plurality of sub-pixels included in the image data is included in an in-focusing region that is focused or an out-focusing region that is not focused; and an interpolator configured to perform demosaicing with respect to a sub-pixel included in the in-focusing region by using a first algorithm and perform the demosaicing with respect to a sub-pixel included in the out-focusing region by using a second algorithm, according to a result of the region determination, wherein, when the demosaicing with respect to the sub-pixel included in the in-focusing region is performed, one or more peripheral sub-pixels having phases that are different from a phase of the sub-pixel, on which the demosaicing is performed, are used.