The technique of the present invention ensures generation of an image file, in which image data and additional data are included, with the confidentiality of specific data kept.An image output system outputs the image data, which is generated in a digital still camera DSC 12, with a color printer 20. The DSC 12 encrypts image processing control data, which is preset by the manufacturer, and generates the image file, in which the image data and the encrypted image processing control data are included. The color printer 20 decodes the image processing control data included in the image file, performs image processing based on the image processing control data, and thereby outputs an image.