Watermarking 3D Models

Tato diplomová práce se zabývá vkládáním vodoznaků do 3D modelů, které jsou reprezentovány polygonální sítí. Jejím cílem je zvolit vhodnou metodu na vkládání/extrakci vodoznaku do/z 3D modelů a vytvořit nástroj, který ji bude implementovat. Pro řešení jsem zvolila metodu spektrální komprese sítě z článku Watermarking 3D models using spectral mesh compression. Tato metoda je nezřetelná, informovaná, detekovatelná a robustní vůči geometrickým transformacím, adaptivnímu náhodnému šumu, vyhlazování a zjednodušení sítě modelu, kompresi a oříznutí.  Nástroj umožňuje vkládání vodoznaku do načteného modelu, modifikovat model a extrahovat vodoznak z modelu. Testování nástroje jsem prováděla na sadě pěti modelů rozdílných svojí velikostí, tvarem a hustotou bodů. Výsledný nástroj vkládá vodoznak složený ze 4 znaků, který dokáže detekovat jak z nepoškozených modelů, tak z modelů napadených. Mezi útoky, vůči kterým je vodoznak robustní, patří posun, rotace, změna měřítka, aditivní šum, oříznutí a jejich kombinace.Goals of this work are to summarize the process and existing methods of 3D models watermarking, to choose relevant methods for embedding/extraction of a watermark to/from 3D models. The final solution is based on Spectral Mesh Compression technique. This method is robust, imperceptible and informed. The embedded watermark is detectable and robust against geometrical transformations, added random noise, mesh smoothing and simplification, compression and cropping.  The realized tool allows a user to embedding watermark into the mesh, modify the mesh and extraction of a watermark from mesh. Testing was conducted on a set of 5 models differing in size, shape and density of points. The resulting tool inserts a watermark composed of four characters that can detect both undamaged models and the models affected. Among the attacks against which the watermark is robust, include transformations, rotation, scale, adaptive random noise, and combination of this.

Robust digital watermarking techniques for multimedia protection

The growing problem of the unauthorized reproduction of digital multimedia data such as movies, television broadcasts, and similar digital products has triggered worldwide efforts to identify and protect multimedia contents. Digital watermarking technology provides law enforcement officials with a forensic tool for tracing and catching pirates. Watermarking refers to the process of adding a structure called a watermark to an original data object, which includes digital images, video, audio, maps, text messages, and 3D graphics. Such a watermark can be used for several purposes including copyright protection, fingerprinting, copy protection, broadcast monitoring, data authentication, indexing, and medical safety. The proposed thesis addresses the problem of multimedia protection and consists of three parts. In the first part, we propose new image watermarking algorithms that are robust against a wide range of intentional and geometric attacks, flexible in data embedding, and computationally fast. The core idea behind our proposed watermarking schemes is to use transforms that have different properties which can effectively match various aspects of the signal's frequencies. We embed the watermark many times in all the frequencies to provide better robustness against attacks and increase the difficulty of destroying the watermark. The second part of the thesis is devoted to a joint exploitation of the geometry and topology of 3D objects and its subsequent application to 3D watermarking. The key idea consists of capturing the geometric structure of a 3D mesh in the spectral domain by computing the eigen-decomposition of the mesh Laplacian matrix. We also use the fact that the global shape features of a 3D model may be reconstructed using small low-frequency spectral coefficients. The eigen-analysis of the mesh Laplacian matrix is, however, prohibitively expensive. To lift this limitation, we first partition the 3D mesh into smaller 3D sub-meshes, and then we repeat the watermark embedding process as much as possible in the spectral coefficients of the compressed 3D sub-meshes. The visual error of the watermarked 3D model is evaluated by computing a nonlinear visual error metric between the original 3D model and the watermarked model obtained by our proposed algorithm. The third part of the thesis is devoted to video watermarking. We propose robust, hybrid scene-based MPEG video watermarking techniques based on a high-order tensor singular value decomposition of the video image sequences. The key idea behind our approaches is to use the scene change analysis to embed the watermark repeatedly in a fixed number of the intra-frames. These intra-frames are represented as 3D tensors with two dimensions in space and one dimension in time. We embed the watermark information in the singular values of these high-order tensors, which have good stability and represent the video properties. Illustration of numerical experiments with synthetic and real data are provided to demonstrate the potential and the much improved performance of the proposed algorithms in multimedia watermarking