Comparison of two wavelet based image watermarking schemes
This paper presents two semi-blind watermarking techniques, based on sets of significant wavelet coefficients, in the three lowest detail subbands of a cover-image. The first method modifies the magnitude of triplets of significant coefficients, according to a sequence of information bits. We show that multiple marks can be embedded in an image. The second method considers rectangular blocks of coefficients, and a uniform quantization-based watermarking scheme. The extraction algorithm requires one to know the position of the sets of watermarked coefficients in order to retrieve the hidden sequence of information bits. Experimental results show the robustness of the two methods, to different kinds of classical signal processing attacks.