1. A method for controlling a user interface of a display device using a gesture, the method comprising: detecting a gesture that sets a region of an image displayed on a display, the set region of the image being a subset of the image and a boundary of the set region of the image being defined by the gesture; at a time when the region of the image is set, detecting motion of an input unit related to modifying the set region of the image; and modifying, by a controller, an image configuration of the set region of the image according to the detected motion.