Nested object watermarking

Annotation watermarking is an application of watermarking where information about a cover or a part thereof are embedded in the cover itself to link both directly together. In earlier work we introduced Nested Object Annotation Watermarking as a special case, where the semantic, shape and hierarchical relations between the depicted nested objects are embedded in the area of each object only. As these regions can be anywhere and may be composed of any shape there is very limited a-priori knowledge for synchronization, which results in a higher complexity and ultimately in a higher error-proneness. In general an exhaustive search strategy for proper block to reconstruct the shape suffers from the intrinsic combinatorial explosion of this process. Therefore in earlier work, at first we focused on rectangular embedding schemes with a block luminance algorithm, a steganographic WetPaperCode algorithm, a rectangular and finally a polygonal Dual-Domain DFT algorithm. In this paper we review and compare these algorithms. For the latter one we also show the influence of several parameters, present our idea of a method to reduce the combinatorial explosion by collating the paths in the search tree, and show that our new synchronization approach surpasses our former rectangular method in terms of correct retrievals, despite its higher complexity.