I just received the latest issue of the print version of Optical Engineering in the mail. It has a paper on storing metadata in images that is related to some work I described recently, namely Rob Tow et al.'s glyphs, and the watermarking and steganography work by Gaurav Sharma et al. respectively Robert Ulichney et al.
The citation is: Jen-Chang Liu and Hsiang-An Shieh, "Toward a two-dimensional barcode with visual information using perceptual shaping watermarking in mobile applications", Opt. Eng. 50, 017002 (Jan 21, 2011); doi:10.1117/1.3529430.
The link is: http://dx.doi.org/10.1117/1.3529430.