1. A method for modifying an image displayed on a display device, the method comprising: detecting a first gesture that involves motion of an input unit that defines a closed curve and that sets a region of the image displayed on the display device, the image displayed on the display device comprising the set region of the image and the closed curve defining a boundary of the set region of the image; at a time when the region of the image defined by the closed curve and set by the first gesture is set, detecting a second gesture that involves motion of an input unit related to modifying the set region of the image defined by the closed curve, wherein detecting the second gesture that involves motion of the input unit related to modifying the set region of the image defined by the closed curve comprises detecting whether motion of the input unit is approaching the display device or departing from the display device; modifying, by a controller, the set region of the image defined by the closed curve according to the detected motion of the second gesture by modifying a center of the set region of the image defined by the closed curve to appear to move upwards based on detection of the input unit departing from the display device or modifying the center of the set region of the image defined by the closed curve to appear to move downward based on detection of the input unit approaching the display device; and generating a new image based on the image and the modifying of the set region of the image defined by the closed curve according to the detected motion of the second gesture, wherein the new image comprises the image and the modified region of the image defined by the closed curve such that the modified region of the image remains within the closed curve defining the boundary of the set region.