Study Of Watermarking Algorithm For Image Based On Biorthogonal Wavelet

Digital watermark is a new direction in the information security field. It's a new technology which can protect copyright and authentication source. The author's personal copyright information can be embedded in the products. But we can't percept it, only special software can pick it up.In this dissertation, the application of digital watermark technology has been studied in the round. Adaptive digital watermark based on biorthogonal wavelet transform was introduced. First of all, background, meaning, domestic and international current situation and problem of existing of watermark are described. Then, basic problems such as the essential feature and principle of the digital watermark, etc. are introduced. The basic frame of the digital watermark system is generalized. The common digital watermark algorithms at present are generality introduced. Subsequently, the preconditioning method of the watermark is introduced. The preconditioning of the grey level picture is mainly compression of the grey level picture and the shuffle technology of the picture. Then, the theory of wavelet transformation is recommended in detail. Finally, digital watermark algorithm for image based on biorthogonal wavelet is proposed.In this dissertation, grey level picture is watermark. The grey level picture is pretreated such as compress, shuffle and two value preconditioning;it is stalwart in order to strengthen the watermark. Consider the performance when the picture is resolved and recombined, select for use resolve coefficient Nr =2 and reconstruct coefficient Hd = 6 biorthogonal wavelet (Bior2.6). The original image is resolved into three layers and four belts by Bior2.6. The watermark is adaptive inserted into low frequency coefficient and intermediate frequency coefficient of wavelet. The algorithm conquers the shortcoming of low frequency coefficient always excluding in the past.Experiments results shows that this algorithm can against widely varying signal distortions (such as sharp, smooth, excision and Gaussian noise), compression and have good robustness.