A DWT-DCT based blind watermarking algorithm for copyright protection

Digital watermark technology is used to protect the legal owner´s copyrights. We propose a blind watermarking algorithm combination of Discrete Wavelet Transform (DWT) and Discrete Cosine Transform (DCT). The watermark is scrambled by Arnold and embedded in a spread spectrum pattern using pseudo random. The block-based DCT transform of DWT LL sub-band is computed and the pseudo random sequence of the watermark bits are embedded in the mid frequency coefficients of the corresponding DCT blocks. Using DWT prior to DCT to provide better imperceptibility and higher robustness against signal processing attacks. Experimental evaluation results show that combining the two transforms improved the performance of the watermarking algorithm based solely on DCT transform.