In an image generation apparatus 10, an input information obtaining section 50 obtains contents of a user operation from an input apparatus 14. When two images are composited, an image data generating section 52 switches a space of image data according to a situation and stores data of images composited in the space in a frame buffer 56. A format control section 54 sets a data format corresponding to the determined space in the frame buffer 56. An output section 58 outputs the data read from the frame buffer 56 as video signals corresponding to a display 16.