Images having been subjected to image processing optimal for each user or each output device are obtained. Correction function calculation means calculates correction functions for correcting image data sets for each user ID or for each device ID, and correction function storing means stores the calculated correction functions. When the image processing is carried out on the image data sets, the correction functions corresponding to the user ID or the device ID added to the image data sets are searched for and correction parameter calculation means calculates correction parameters based on the correction functions. The image processing is then carried out on the image data sets according to the correction parameters to generate corrected image data sets.