An optimal detector structure for the Fourier descriptors domain watermarking of 2D vector graphics

Polygonal lines constitute a key graphical primitive in 2D vector graphics data. Thus, the ability to apply a digital watermark to such an entity would enable the watermarking of cartoons, drawings, and Geographical Information Systems ( GIS) data in vector graphics format. This paper builds on and extends an existing algorithm that achieves polygonal line watermarking by modifying the Fourier descriptors magnitude in an imperceptible way. Watermarks embedded by this technique can be detected in rotated, translated, scaled, or reflected polygonal lines. The detection of such watermarks had been previously carried out through a correlator detector. In this paper, analysis of the statistics of the Fourier descriptors is exploited to devise an optimal blind detector. Furthermore, the problem of watermarking multiple lines, as well as other implementation issues are being addressed. Experimental results verify the imperceptibility and robustness of the proposed method.