Study Of Robust Watermarking Algorithm Based On Dual Transform Domains

With the rapid development and increasing popularity of the Internet, more and more people publish their works, transfer data and share information by Internet, which make the storage, reproduction and distribution of multimedia data become easier. Internet, to facilitate the communication for people, at the same time, also presents new challenges for copyright protection of multimedia. The casual tampering, wanton dissemination of digital works, even acts of copyright infringement, has given rise to people’s attention. The digital copyright issues need to be resolved.As an effective means of protecting digital copyright, digital watermark offers new ideas to combat piracy and protect intellectual property of multimedia. The robust digital watermark technique in digital content protection-related areas has good application value, such as pirated tracks, copy control and copyright protection. But the current research of robust watermarking technology has not reached the step of applications. There are many technical challenges to be addressed. In order to increasing the robustness of watermark, Particle Swarm Optimization algorithm was applied to the digital watermarking embedding algorithm.Firstly, one-level wavelet decomposition was employed for the two-dimensional carrier signal by using the characteristics of wavelet multi-resolution analysis, and then the low-frequency and middle-frequency coefficients were extracted. After dividing the coefficients into small blocks, discrete cosine transform was used for each block coefficients.Then, adaptive quantization algorithm was designed. The optimal embedding positions in the two dimensional space of carrier signal were determined dynamically by Particle Swarm Optimization algorithm, and the coefficients in the optimal embedding positions were also extracted. According to the characteristics of these coefficients, the optimal quantization step sizes were determined dynamically in three dimensional spaces. Finally, the watermark was embedded into watermarking vector adaptively by using the optimal embedding positions and the optimal quantization step sizes, the watermarked vector was received.The experimental results show that compared with traditional watermark algorithms, the presented robust watermark algorithm based on dual-transform domain not only eliminate the block effects that might arise in the transform process, but also make full use of Particle Swarm Optimization algorithm to determine the optimal embedding positions and optimal quantization step sizes of the watermark embedding algorithm. It implements adaptive embedding and increases non-sentience and robustness of watermark. A series of attacks experiments and comparative experiments show that the performance of the proposed algorithm is better than traditional algorithm.