Research On Digital Watermarking Algorithm Based On Wavelet Transform

Digital watermarking has developed rapidly since years ago. The use of it is more and more wider and the research on it has been paid more and more attention.Wavelet analysis is a very valid analyzing means. Recently, with the development and improvement of wavelet theory, wavelet analysis has been applied to many fields and become one of the popular tools for researchers and scientists. At the same time, wavelet theory has been applied to digital watermarking successfully and much new algorithm of digital watermarking is formed.As we all know, digital watermarking is used for digital works. There are kinds of digital works, such as video, audio works, digital image and so on. In this thesis, we only talk about the digital image.In this thesis, I introduce the purpose and meaning of my study in this field and also introduce the definition, characteristic, class and use firstly. Then I introduce the primary watermark attacks and their relevant Countermeasures. And then I introduce the basic theories of wavelet transform, including continue wavelet transform, delete wavelet transform, multi-resolution analysis and Mallat algorithm and so on.The later three chapters are the main parts of this thesis. In the fourth chapter I introduce the virtues of digital watermarking based on wavelet transform. Then according to the characteristics of human vision system especially that different color it has different sensitivity, I put forward three methods to embed a digital watermark. According to these three methods, I bring forward an algorithm which based on LSB further. At last, make sure that which is the best among the three methods.In the fifth chapter, another algorithm is put forward according to the three methods. Firstly, in this chapter I discuss the place where to embed the digital watermark. After comparison, I educe that after wavelet transform when embedding the low frequency information of a watermark to the intermediate frequency of an original image the result is best. Finally, educing which is the best method among the three.The results of the three methods are not so good, though we can get the conclusion that the first method is the best. In the fourth chapter and the fifth chapter the third method are a little different. Obviously, the third method in the fourth chapter is better than the fifth's. So I change the third method in the fifth chapter according to the third method in the fourth chapter. After changing the results show that the changed third method in chapter five has the best invisible property and robust property. At last we get the conclusion according to chapter four and chapter five.The algorithm of the sixth chapter is the improved algorithm of the fifth chapter. I change the secret digital watermarking algorithm into the semipublic digital watermarking algorithm. Obviously, after changing the cost of saving data is cut and also the protecting mechanism is improved a lot. The semipublic digital watermarking algorithm is more bread-and-butter and the use of it is broader.The seventh chapter is the conclusion and prospect for this thesis. There are some shortcomings of this thesis to be developed. Also in this chapter I describe the future development of digital watermarking technology.