A first image-data processing unit unifies characteristics of input image data so that the image data is usable in an image writing unit and an external device, stores characteristic-unified image data in a storing unit, and changes an attribute of supplemental information according to an image input condition. When converting target image data into image data with characteristics suitable for outputting to the image writing unit and an external interface unit, a second image-data processing unit makes the stored image data be reusable in the image writing unit and the external device by performing an image processing based on the supplemental information.