Frequency domain infrared watermarking for printed CMYK image

A new framework is proposed to embed watermark through alternating frequency components of the black plane of a printed CMYK image according to the watermark message, and then decode the watermark with an infrared (IR) scanner. This framework leverages the facts that a given color can be produced by multiple combinations of CMYK quadruplets and the standard four-color printing materials have very different infrared transmission characteristics. Carbon-based black toner is a good absorber of infrared light, while the other color toners are almost transparent in the infrared region. In the proposed framework, a watermark message is first embedded in the black plane. After that, a color adjustment step is followed to modify the CMY planes in order to minimize visibility of the watermark. Thus, the proposed method has the advantage of low visual noise caused by watermark embedding. In addition, it is available for “blind decoding”.