Image forming system with external apparatus, image forming apparatus and projector

Abstract

Provided is an image forming system that simply and securely protects printed matter that is not so important, but that the user does not wish others to view. An external apparatus receives a simple-security setting for image data for which there is a printing instruction, includes the simple-security setting in the printing instruction, and transmits the printing instruction to an image forming apparatus. The image forming apparatus, when a simple-security setting is included, adds a mark image to the image data for which there is a printing instruction, and prints the image data. A projector, by an imaging unit, captures an image of the discharge tray, and when a mark image is detected, generates a projection image on which a security image is arranged, and projects the projection image toward the discharge tray.