COLOR IMAGE FORMING DEVICE

PROBLEM TO BE SOLVED: To provide a color image forming device by which tracking patterns for forgery preventions including electronic watermark data, can be added to a printed image which it outputs. SOLUTION: An electronic watermark data discriminating circuit 206 discriminates electronic watermark data from printing data transmitted from a host device 210. The printing data other than the electronic watermark data discriminated by the electronic watermark data discriminating circuit 206 are converted into print image data by a print image generating section 301 and are transmitted to an engine I/F 208. A tracking data generating circuit 207 generates tracking patterns by adding the inherent data of a color image forming device in a nonvolatile memory 204 to the electronic watermark data. The engine I/F 208 composes the print image data which are transmitted from the host device 210 and are generated by a CPU program of the print image generating section 301, and the tracking data patterns and outputs the composed image to a printer engine 211.