Provided herein are teachings directed to the creation of moiré-based auto-stereoscopic watermarks in rendered images. By choosing different halftone structures, which differ by having different spatial frequencies for each of two delineated partitions in an image, it becomes possible to embed arbitrary binary patterns into printed documents as digital watermarks. The invisible watermarks become moiré auto-stereoscopic images when the prints are viewed through an overlaid transparency “decoder” suitably prepared by virtue of being rendered with a uniform halftone structure having the correct special frequency in relationship with the partition frequencies employed in the printed document.