| As a main method of digital image copyright protection and a new information hiding method, digital image watermarking has been rapidly developed in recent years. Robust watermark is a rather difficult research field. It is well known that watermark is robust enough if it is embedded in low frequency of transform domain. In face of many transform domains, we are often puzzled where to embed our watermark. In this paper, we have tested low frequency coefficients of several usual transform domains, and draw a conclusion that the optimal embedded domain is blocked layered DCT (proposed by this paper). Finally, we propose a new robust and blind watermark algorithm based on blocked layered DCT.In the first chapter of this paper, we give an overview of digital watermarking, including: classification, algorithms, principle, usual attack ways, detection, research topics. A new scrambling technology is proposed in this chapter.In the second chapter, we have introduced usual transform domains: including blocked discrete cosine transform, discrete wavelet transform. We also mentioned related algorithms and principle. In the example, a new blind watermarking algorithm based on DCT is proposed, in which a binary picture is embedded. The method is coefficients of low frequency divided by 14. Then, these quotients are divided by 2 in order to use the remainders. The experimental result shows that the embedded watermark with proposed algorithm is invisible and it is robust enough that it can resist attacks of the commonly used image processing. At the same time, the experimental result shows that our scrambling technology is also effective. At the end of the chapter, we propose the improving algorithm which can increase the quantity of embedded watermark.In the third chapter, We have tested low frequency coefficients of usual transform domains: Such as discrete cosine transform, discrete wavelet transform, layered DCT and blocked layered DCT which is proposed by this paper. The experimental result...
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