| In the age of information technology and multimedia digital prosperity,malicious spread and piracy have become global phenomena.Therefore,the demand for digital content protection is unstoppable,among which digital watermarking technology is being widely used to solve many problems in the field of digital copyright protection management and multimedia security.Since most copyright protection methods can embed watermark with less information,this paper takes the dual-color image with more information as the main object of research to overcome the shortcomings of existing color image watermarking methods in the aspects of robustness,real time,security and so on,four kinds of dual-color image digital watermarking methods are designed and completed by using the quaternion,the real structure-preserving algorithm,image correction algorithm,fusion domain algorithm,compound chaotic mapping and other technologies to achieve embedding and blind extraction of color watermark images.The main research contents are described as follows:(1)Owing to the correlation between color channels and unsynchronized watermark embedding are ignored by the existing color image digital watermarking methods,a novel watermarking method using quaternion singular value decomposition is proposed for protecting the copyright of color image.According to the feature that the quaternion-based image processing can capture the correlation between color channels and integrate three-color channels,the maximum singular value of the diagonal matrix is quantified for embedding watermark information.Meanwhile,for solving the problem that the singular value of low brightness image is still zero after embedding the watermark,this method adds the judgment of extreme pixel values,so as to improve the integrity of the extracted watermark.Finally,an image correction algorithm is also added to further improve the robustness against geometric attacks added in this method.Many experiments show that the method has good watermarking performance on the whole,that is,the embedded color watermark is not easy to be detected,and this method can effectively resist some common image signal processing attacks and geometric attacks.(2)Owing to the existing quaternion-based watermarking methods have high computational complexity,the real structure-preserving quaternion Schur decomposition is used to design a new dual-color image digital watermarking method for meeting the real-time requirement.According to the characteristic that the quaternion operation of the quaternion matrix is equivalent to the real number operation of its real representation,the real structure-preserving algorithm is used to perform the quaternion Schur decomposition and the watermark is embedded by adjusting the coefficient pairs with high correlation.At the same time,this method adopts compound chaotic mapping to encrypt the watermark more uniformly and effectively enhance the security.Finally,to solve the problem that watermark bits cannot be correctly extracted when all pixels of the embedded block are zero,the dithering noise and pixel fine-tuning method are added for enhancing the robustness to a certain extent.Many experiments and analysis show that when the actual embedding rate and invisibility are consistent with other methods,the method has strong robustness and high security,and the running time of this method is about 20 times shorter than that of Matlab quaternion toolbox.(3)Owing to the existing image watermarking methods underestimate the influences caused by geometric attacks,URV decomposition is used to design a dual-color image digital watermarking method.After considering the relationship between each channel,the watermark is embedded into the URV decomposition coefficient by using quantization index modulation technique based on variable quantization steps.At the same time,this method proposes an image correction algorithm that can quickly find the image corners,correct any quadrilateral image and reduce the sawtooth effect,which can effectively improve the robustness against some common geometric attacks.Finally,the compound chaotic mapping is used to generate two chaotic sequences for pixel-level scrambling and bite-level diffusion of the watermark,which effectively improves the security.Many experiments show the presented method is strong to resist signal processing and image geometric processing under the condition of the same actual embedding rate.(4)Owing to the spatial domain watermarking methods have poor robustness and the frequency domain watermarking methods have high running time,LU factorization is used to design a fusion-domain dual-color image digital watermarking method.By deducing the distribution relationship and calculation method between the changed special matrix elements after LU factorization and spatial image pixels,the watermark embedding and extraction can be completed directly in the spatial domain without the real frequency domain conversion,which has the advantages of two kinds of watermarking and greatly improves the real-time performance while ensuring the robustness of the algorithm.At the same time,this method proposes an effective image correction algorithm,which uses straight line detection to locate image vertices more accurately,corrects arbitrary quadrilateral image,and uses the idea of fast approximation anti-aliasing to carry out anti-aliasing operation.Many experiments show the running time can be shorten nearly 63% under the requirement of good image quality,and its ability to resist some common image processing attacks has been significantly improved.In this paper,digital watermarking methods are designed and implemented by using a variety of technologies,which have different outstanding advantages in other performances on the basis of satisfying good invisibility.These methods can not only meet the different needs of copyright protection occasions,but also provide theoretical basis and technical support for the copyright protection of color digital images under the current development environment. |
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