According to one embodiment, an image processor has a resolution detector, a first resolution changing unit, a second resolution changing unit, and a resolution changing controller. The resolution detector detects a resolution of an input image data. The first resolution changing unit changes the detected resolution into a resolution that is higher than the detected resolution. The second resolution changing unit changes the detected resolution coinciding with a predetermined input resolution into a predetermined output resolution that is higher than the detected resolution so as to provide the input image data with a definition higher than a definition of an output image data provided with the resolution changed by the first resolution changing unit. The resolution changing controller activates the first resolution changing unit to change the detected resolution that does not coincide with the predetermined input resolution into the predetermined input resolution, and activates subsequently the second resolution changing unit.