A DWT-based image watermarking algorithm
In this paper, a new embedding strategy for DWT-based watermarking is proposed. Different from the existing watermarking schemes in which low frequency coefficients are explicitly excluded from watermark embedding, we claim that watermarks should be embedded in the low frequency subband firstly, and the remains should be embedded in high frequency subbands according to the significance of subbands. We also claim that different embedding formula should be applied on the low frequency subband and high frequency subbands respectively. Applying this strategy, an adaptive algorithm incorporating the feature of visual masking of human vision system into watermarking is proposed. In the algorithm, a novel method to classify wavelet blocks is presented. The experimental results demonstrate that the watermarks generated with the proposed algorithm are invisible and robust against noise and commonly used image processing techniques.