Digital Images And Three-dimensional Geometry Model Watermarking Technology Research

The multimedia information security problems including copyrights piracy emerged as side effects over network. In this dissertation, we study the technologies of digital image watermarking and 3D model watermarking. The main contributions of this dissertation are:A Novel Detection Strategy In Blind Image Watermarking AlgorithmGenerally, the traditional detection strategy corresponding to embedment model I=I+ aW has its limitation. First, we treat the watermark information as noise for an image and expand the noise before detection. Then, we find the corresponding data in the frequency-domain and adjust them according to our relative minmum principle. Finally, we recover the watermark according to encodement. We also apply the novel detection strategy into the image watermarking algorithm based on Fourier-Mellin transformation, which is trong to geometric invariants. The original image was not required for extracting the embedded marks.A Method to Construct "Zero-Watermarks" "Zero-Watermark" is a new concept that donot change the original image during watermark embedment. It is difficulit to construct a strong "Zero-Watermark" because "Zero-Watermark" is weaker than the traditional watermark. The geometric invariant which is produced by Fourier-Mellin is computed and some of them are taken as "Zero-Watermarks". The experimental results show that our "Zero-Watermark" is effective and robust.A Valid Blind Watermarking Algorithm On Image The images that have a lot of white pixels usually can produce a lot of overflows after being embedded the watermark. The algorithm embeds the watermarking signal modulated on some fix positions that keep some distance from each other. Some decimals are added to the image-signed and different parameters are mbedded for different images. The experiments show that it is transparent, robust, accurate and cost-efficient.A 3D Mesh Watermarking Algorithm based on Spherical ParameterizationFirst, we transformed the coordinate signals of the 3D triangular mesh into spherical signals using a global spherical parameterization and an even sampling scheme. Then, spherical harmonic transformation is used to generate some data for embedding watermarks. As a result, the watermarks can be embedded in the Fourier-frequency domain of the original mesh. Experimental results showed that our watermarking algorithm is robust since watermarks can be extracted without mesh alignment or re-meshing under a variety of attacks. The processing is needed when the watermarked mesh goes through vertexes reordering and simplification.A Public Mesh Watermarking Algorithm The watermarked mesh is obtained by using a public image watermarking algorithm to embed a watermark in a gray image. First, the watermarked image minus the original image is the watermark information. According to the addition property of the Fourier transform, a change of spatial domain will cause a change in the frequency domain, which will allow watermarks to be extracted from the watermark information. Then, the watermark information is scaled down and embedded in one part of the x-coordinate of the original mesh. Thus, the watermarked mesh is obtained. Experimental results prove that the algorithm is resistant to a variety of attacks.Watermarking Subdivision Surfaces and NURBS Surfaces For subdivision surface, some 3D mesh watermarking algorithm is used and the watermarked subdivision surface is obtained. For NURBS surface, the watermarks are encoded and embedded into some intervals of the knots of the oringnal NURBS suface. The shape of the oringnal NURBS surface is not changed after being watermarked.