Wavelet-based watermarking algorithms: theory, applications and critical aspects

The copyright protection of digital images is a critical element for multimedia applications on Web, electronic libraries and virtual image galleries. Since the middle of the nineties, digital watermarking techniques have been proposed as a streamlined solution to solve the copyright problem. In this article we present the difficulties occurred during the construction and the experimentation of our wavelet-based watermarking algorithm. In fact we faced the classical watermarking problems such as computational cost, imperceptibility and robustness. In addition to these critical aspects we had to resolve problems concerning the application of watermarking techniques on a real database Web gallery.