An image processing system enabling luminance regulation depending on displayed images is provided by a projector, the projector including: a signal input section which input an image signal; a signal output section which outputs a corrected image signal; an image projecting section; a correction table storage section which stores a correction table showing the relationship between a correction amount and a position in an image; an instruction input section which inputs instruction information representing a correction instruction from a user; and a luminance regulating section which corrects a luminance value of the input image signal to make a luminance value in a central portion of an image lower than the current luminance value of the center portion when uniformity improvement of luminance values in central and marginal portions of the image is desired, or corrects that to make a luminance value in a marginal portion of an image lower than the current luminance value of the marginal portion when emphasis of a central portion of the image is desired, based on the correction table and the instruction information.