Image protection via watermarking on perceptually significant wavelet coefficients
A new scheme to search perceptually significant wavelet coefficients for effective digital watermark casting is proposed in this research. Unlike other watermark casting algorithms, which select a fixed set of DCT or wavelet coefficients in the frequency domain, we use an adaptive method to find significant subbands and a number of coefficients in these subbands. The resulting method is image dependent. Furthermore, the threshold of the selected subband is used as one of the energy weighting factors in the generation of a broadband watermark so that it cannot be easily damaged by frequency-selective filtering, DCT or wavelet based compression attack.