Based On Wavelet Digital Watermarking Algorithm Design And Implementation

The rapid development and wide application of multimedia and network technology have made the storage, processing and distribution of digital multimedia products much easier and faster, and the digital copyright has become more important at the same time. Encryption techniques can be used to protect digital data. However, after the decryption of the data, the data is in the clear and no longer protected. Digital watermarking is another effective solution that is regarded as the last line of defense. This thesis aims at some important problems of watermarking techniques. The main research efforts are list as follow.Firstly, the states, basic model, characteristics, classification and applications of the digital watermarking techniques are introduced. Strategies of current watermarking techniques are broadly investigated. The current methods of the design, generation and pretreatment of watermark are listed out. The various attack methods are introduced and fully analyzed and several directions of development of digital watermarking at next stage are proposed. Secondly, we introduce the relevant theory of wavelet decomposition of images and analyze characteristics of wavelet coefficients. Like a scalar wavelet case, the wavelet decomposition provides us a multi-resolution representation of an image. However, there are four different coefficient sub-blocks in the same direction and in the same resolution. In addition to a wavelet has some advantages in comparison to a scalar wavelet, such as short support, orthogonality, and symmetry. Then, the IDWT theory, the HVS (human visual system) theory and chaos system are applied to digital watermarking embedment.For copyright certification and integrality authentication on digital images,using of texture of images, this paper presents adaptive robustness watermarking algorithm and semi-fragile algorithm capable of tamper location.Robustness algorithm: considering the features of human visual system (HVS) and the wavelet transform, a new adaptive watermarking algorithm is proposed. The original image is decomposed by wavelet transformation. Then wavelet coefficients are organized in order to form wavelet blocks. Based on several parameters with the features of human visual system (HVS), they are classified into several classes. Watermark components with different strength are embedded into different wavelet blocks based on the results of classification and the features of wavelet transform. Experimental results demonstrate that the algorithm is robust to attack on data image.Semi-fragile algorithm: an approach of semi-fragile watermarking, which is based on DWT and capable of tamper location, is presented here. In this method, after the host image was DWT-decomposed, we choose location for watermark insertion by sorting low and intermediate frequency coefficients. By introduction of public-key algorithm in modern cryptography, we insert content-based watermark. Experimental results demonstrate that the algorithm is imperceptible, blind, and robust to JPEG compression, sensitive to spiteful tamper such as cut and cut-replace and so on, precise to tamper localization.All experiment data on basis of abundant experiments is drawn out for the performance analyses. The experimental results show that the imperceptibility and robustness of these methods can be guaranteed. Finally we review entire work. Something need to research in the next step is pointed out. And we suggest the direction for the future research of watermarking.