An image processing apparatus implements appropriate image processing on image data stored in a storage unit of the image processing apparatus easily and efficiently, and distributes the image data to an external apparatus. An image format conversion unit implements image processing such as resolution conversion processing, filter processing, γ correction processing, and halftone processing on image data stored in an HDD serving as an image data storage unit so that the image data conform to conditions, such as image quality and format, specified by an external client apparatus. The image-processed image data are then distributed to the external client apparatus.