Image and watermark registration

This paper addresses issues concerned with image registration, where the image contains an invisible watermark. We present a selection of registration masks which can be deliberately overlaid on a watermarked or raw image, allowing the recovery of the correct registration. For visible masks at high signal-to-noise ratio, the window property is useful. For invisible masks, the (aperiodic) autocorrelation peak to sidelobe ratio is important, as is the local pattern balance. Methods of combining watermarks with registration patterns are presented. The masks studied include: perfect maps, perfect even and odd binary arrays, m-arrays and quasi-in-arrays. (C) 1998 Elsevier Science B.V. All rights reserved.