Research On Color Image Blind Watermarking Algorithm Based On NSCT

With the rapid development of Internet technology and multimedia information processing technologies,digital images have been widely spread on the Internet,copyright infringement and information tampering of which are occurring frequently.How to ensure the secure transmission of digital images between networks has become an urgent issue in the digital era.Digital image watermarking technology,which is the most effective method on the issue of copyright protection of image,has attracted more and more attention at present.However,most of proposed robust image watermarking algorithms are to mark grayscale images,and few of them are for color image.Most algorithms need original images or watermarking images when extracting watermarks,which is limited to achieve blind watermark extraction.The focus of this thesis is proposing a robust blind digital watermarking algorithm for color images.The work is as follows:(1)Based on the proposed QR Decomposition watermarking algorithm,we propose a color images watermarking algorithm based on Non-Subsampled Contourlet Transform(NSCT)and QR decomposition,which improves the watermarking capacity of watermarking algorithm and the correct extraction rate of watermarking information without attack.In order to realize the blind watermark extraction,the algorithm uses Quantization Index Modulation Technology when embedding a watermark.Extracting watermark does not need the original image or the original watermark.This algorithm is suitable for more scenarios.Then,compared with other literature algorithms,the watermark's invisibility and robust of the proposed algorithm are well balanced when the robustness is strong under most attacks.(2)In order to apply the watermarking algorithm to the actual scene better,we should make compromise with efficiency,invisibility and robustness of the watermarking algorithm.Therefore,a color images blind watermarking algorithm based on Non-Subsampled Contourlet Transform and Hessenberg decomposition proposed in the thesis performs more efficiently.The experimental results show that this algorithm ensures the good invisibility of the watermark and robustness under certain attacks and and it improves the efficiency of the algorithm compared with the first proposed watermarking algorithm based on NSCT and QR decomposition.(3)To avoid the watermark information leakage caused by cracking the algorithm,we encrypt the watermark information before embedding the watermark information into the carrier image.The color watermark image is decomposed into R,G,and B three-channel component images,which are encrypt based on both the Arnold Scrambling Transformation and the random sequence.The watermark information is more secure under such multiple encryption.(4)Simulaing the proposed watermark algorithm in matlab,the thesis analyzes experimental results and compares them with other literature algorithms on the watermarking invisibility and robustness.Finally,the proposed algorithm is applied to the website,the experiments are conducted with actual images on the website.