Spectral visible edge marking for steganography or watermarking

A print media having printed image or text or both and visibly hidden content embedded in the printed images or text or both image content, comprising:

• the image content printed with one or more visible colorants to provide images or text or both;
• the hidden data provided by selective printing of at least one spectral edge marker material onto at least one image region of the print media to provide visually hidden data, wherein the spectral edge marker material has a substantial spectral absorption just outside the human visible spectrum;
• and
• the hidden data further provided by selective printing of at least one visible colorant to image regions including those having the at least one spectral edge marker material, such that image regions having only the at least one visible colorant and the image regions having the at least one selectively printed spectral edge marker material and the at least one visible colorant are color matched;
• wherein the at least one visible colorant has both a significant visible light absorption and a second spectral absorption, the second spectral absorption being in a bandwidth overlapping with at least a portion of a bandwidth of the spectral edge marker material that has the substantial spectral absorption;
• and
• wherein the density difference provided by the at least one spectral edge marker material and the at least one visible colorant in the spectral region just outside the visible spectrum, as indicated by an optical density difference (ΔD), has an optical density ΔD<0.1.