Research And Application Of Digital Watermarking Technique

Wth the advancement of computer technology and the progresses ofiriformation technology, especially the sharp increase of the Intemet users andfast development of the multimedia technology digitalized products havebecome more and more popular It is much easer for transmitting, copying,tampering and pilfering of digital data. Thus, it is increasingly urgent that how toprotect the copyright of digital data effectively and prevent the pirate of digita1data. As a new tyPe and effective means fOr the protection of digital dat4 muchattention fOcuses on digital watermarks. On the basis of the discussion andinvestigation of digital watermarks, the design and realization of the still imagedigital watermarking systems on the wavelet transform are presented in thisdissertaion.The fundamentals, such as basic concepts, definition, main feature. basicprinciple, classification and the evaluation standard of digital watermarking, aresystematically stUdied in this dissertation. The difference is discussed betweenconventional cryptographic systems and digital watermarking systems also.Besides, the basic definition, orthogonal wavelet and multi-resolution anaIysis,scaling equation and construction equation and the aPplication of MallatarithInetic in the image processing are introduced in the dissertation as well. Anddetail discussion of the aPplication of the theory of wavelet in the digitalwatermarking, especially, the discussion centered on the theory of the two-dimension wavelet decomposition and reconstruction for the still images, aregiven in this dissertation.Fol1owing the introduction of the format of still images, the selection ofwatermark and the choice of the transform, embedding position of the watermark,embedding and extYacting arithInetic of the watermark are discussed. At last anew image-adaPtive Waermarking scheme is brought forward, which takes fulladvatage of the good characters of wavelet bof Orm and human visual systembased on spread spectri theory And the algorithrn has good robusiness andcaPacityBoth the gray - l ev e l - im ag e - adapti ve watermarking system and c o lor- imagewatermarking system based on the image-adaptive watermarking scheme in theYUV color-mode space are implemented. The results of compuler simulationshow that the proposed watermarking methods satisfy the requirements ofrobustness and transparency. This scheme can resist the conunon imageprocessing operations, such as lossy compression, cropping, filtering and scaling.