The Research Of Semi-fragile Watermarking And Resist To Geometric Distortion's Watermarking

Recently digital watermarking gets the rapid development, presently robust to geometric attacks become the hotspot and difficult problem in the research of watermarking.Hereby this text makes the still picture as study object, and put forwards two kinds of watermarking algorithm which robust to geometric attacks. Besides, this text also put forwards a semi-fragile watermarking.The request of semi-fragile watermarking and robust to geometric attacks'watermarking is oppositive, if only the semi-fragile watermarking has a little robustness to common image process, but it must has the capability of checking and locating the unlawful tamper in watermark image. The three kinds of watermarking algorithm make best used of orthogonal transform's character, according to Discrete Cosine Transfor, Lifting Wavelet Transform and Contourlet Transform to put forward this three watermarking algorithm:1. A Semi-fragile Watermarking Algorithm Based on DCT. This algorithm uses DCT merit, and combine the HVS masking character, it makes the built-in watermarking enery distribute the image blocks preferably .In the promise of imperceptible, it has strong robustness.Also it has capability of checking tamper, it can orient 8*8 block in the spatial domain.2. A Robust to Geometric Attack's Watermarking Based on Edge Information and Affine Model. It makes the frame coefficient as edge information in the approximat subband of lifting wavelet transform, Using edge information and affine model to estimate geometric attack.Then the thesis proposes a self-adapt watermarking algorithm robust to geometric attack in DWT domain. In the algorithm, a watermark was embedded adaptively in low band of DWT domain, according to the conceal quality of Human Visual System (HVS). The proposed watermarking algorithm is not only imperceptible but also robust against geometric distortions, such as translating, rotating, zooming, mirroring, transposing and general image attacks.3. A watermarking algorithm robust to geometric distortion in Contourlet domain. It uses the filiation in different resolutions in Contourlet to put forward"important-tree", thereby choose the important coefficients to embed and extract the watermarking. Also it uses image normalization, by calculating and comparing the eigenvalue of original image (the watermark has been embedded) and incept image (attacked image) to resume image and extract watermarking information. The results show this method has good geometrical characters resisting to the attack of plane-vertical flip, rotate and scale.