Based On The Transform Domain Digital Watermarking Technology And Image Compression

In the dissertation,we study two technologies of image processing based on frequency domain.The one is on digital watermarking,the other is on image compressing.The digital media has become a main way for information communication along with the wide use of network and has played an important role in people's life.As side effects of the popularity of digital representation and distribution over network,some individuals or groups copied,transfered,amended and even sold the digital media without the permission of copyright owners,which greatly damaged the copyrights and commercial benefits of owners.Therefor,the problem how protect the copyright has become a hot one in research work.In the dissertation,we mainly study the technologies of digital watermarking. In addition,we study the technology of image compression based on frequency domain.Image compression is one of key technologies of multimedia.It is very important to seek a good method of image compression. Because the wavelet transform has a good local character both in time domain and in frequency domain,it makes up for the deficency of DCT tranform.On the other hand ,the character of multiresolution analysis combines with the human visual system.The coding of wavelet tranform is a hotspot in the research of image compression code.In the technology of digital watermarking ,two new methods on digital watermarking are finished:the first is based on discrete wavelet transform and the second is based on discrete cosine transform.In the first one,after a digital watermarking is preprocessed by image scrambling and bit-plane decomposition,it is embedded into the middle domain of wavelet coefficients through a quantification function.The primitive image isn't needed when the watermarking is extracted,named as blind extracting.In the seconde one,the human visual system is fully considered.The watermarking is embedded into middle domain of DCT coefficients after it is preprocessed.At the same time,the primitive DCT coefficients which the watermarking is embedded into is written into a code file.With the help of the code file,the watermarking is extracted. Experimental results have proved that the two new methods are robust enough to some image attacking processes.In the technology of image compressing,a techniques of tree character plane which is based on discrete wavelet tranform is finished. Since there is a tree structure among the subbands of wavelet tranform coefficients ,a tree character plane can be built. The four-fork-tree coding and the arithmetic coding are applied in the new coding technique. Experimental result has proved that a better result of image compression is got by the new coding technique.