An image reproduction apparatus having a basic function at low cost, and additional functions as an option. The image reproduction apparatus is configured to detect invalid pixels, remove a black streak, and detect a blank document page. The image reproduction apparatus includes a base engine/image data controller that includes a process controller, a RAM used as a work area, a ROM in which operation commands are stored, a video controller that processes image data and controls the flow of image data, and an I/O controller that monitors and controls I/Os of various devices, such as drivers or sensors, wherein those parts are connected via a CPU bus. The image reproduction apparatus can be extended into the form of a digital multifunction device by connecting a controller board to the base engine/image data controller via a parallel bus.