There is provided a data processor for a display device including a display panel having a first resolution. The data processor includes a first mode selector and a player. The first mode selector includes a distance detector, a comparator, and a transmission resolution adjustor. The distance detector may detect a current distance between a viewer and a display surface of the display panel. The comparator determines an amount of change of the current distance from a previous distance. The transmission resolution adjustor determines a second resolution according to a threshold range within which the previous distance falls and the amount of change. The player processes received external image data as intermediate data having the second resolution.