Research On Robust Watermarking Technologies For Digital Images

With the rapid development of computer, multimedia and Internet techniques, the multimedia security becomes an important and challenging research topic. Digital watermarking technique is a new method for digital content protection such as copyright protection, transaction tracking, content authentication, broadcasting monitoring, copy control and secret communication, and becomes an important research area in the field of multimedia security.In this dissertation, a systematical introduction of the applications, classification and background of watermarking techniques is given first. Then the principle of digital watermarking is described with their characteristics and design requirements in different applications being analyzed, before the ways of performance evaluation, attacks and countermeasures are introduced. The work is focused on the key techniques of digital watermarking for images, which include blind detection, robustness, invisibility. The presented study is the current research focus of watermarking techniques. Thus, its research has both the theory and the application value.The main contributions of this dissertation can be summarized as follows:1. Region-based watermarking technique is studied and a watermarking scheme using the region with salient features of the image is proposed. A simple and effective algorithm for extracting the region with salient features is first realized by exploiting the human visual attention model. The watermark is embedded into this region using the part information of the original image, and its invisibility is derived by means of HVS. Watermark can be blindly detected by means of the reference watermark, which is designed during the watermark embedding process. The primary characteristic of the scheme is that, it presents a new idea for the watermarking techniques, by means of which the watermark embedding should exploiting the image region to which human eyes pays more attention. This idea has the evidence based on the human visual attention model and has considered the subjective requirement of the copyright owner. Experimental result shows effectiveness of the proposed methods.2. Salient feature-based watermarking technique is studied. A salient interestpoint-based watermarking scheme is proposed based on the analysis of the recent feature-based algorithms. The primary characteristic of the scheme is that, it exploits the refined pattern recognition techniques to find the robust image feature, by means of which the watermark can be bound with the image content to improve the reliability of the blind detection. The scheme firstly uses an adaptive filter to process the image. Then the popular way is adopted to detect the interest points. The extracted interest points are selected to obtain the robust salient interest points, which are used as a reference for both watermark embedding and detection. Watermark is iteratively embedded into each local region centered at the points. HVS is used for the invisibility of the watermark. The detection performance is analyzed to guide the watermark detection. Experimental result shows the effectiveness of the proposed scheme.3. Spread spectrum watermarking techniques are studied, and a identifier watermarking scheme is proposed. Watermark embedding includes the techniques of error-correct code, direct sequence spread spectrum and wavelet-based HVS model to gain the trade-off between robustness and invisibility of the watermark. The orthogonal wavelet is used in embedding process, and watermark energy can be adjusted by means of HVS with a specific PSNR. Experimental result shows that the scheme improves the robustness of the watermark with a high quality marked image.4. Side-informed watermarking techniques are studied. A side information-based watermarking algorithm is proposed. Watermark embedding includes the techniques of error-correct code, shuffling, extracting the side information from original image and wavelet-based HVS model to gain the robustness and security for the blind d...