Research On Digital Watermarking Technology Of Color Image Against Print-Scan Attack

The advent of the Digital Age has brought great convenience to people's work,study and life.The development and application of multimedia technology has become an important research area that can't be ignored.The problem of protecting the rights of creators and tracking the source of pirated products has become a hot research topic in recent years.As an important branch of multimedia products,color images are easy to be copied,printed,scanned and spread.Therefore,to protect color images against print-scan attack is of important research value.Digital watermarking technology effectively protects the copyright of color image and traces the source by embedding information as authentication information or proof of printing process.Therefore,the research on digital watermarking technology of color image against print-scan attack is of great academic significance and practical value.Due to the printing and scanning process of color images is a complex noise attack process,there are few researches on digital watermarking technology of color image against print-scan attack,which the ability of against print-scan attack should be improved and the adaptability is poor.To solve the above problems,based on the analysis of the changes before and after the printing and scanning process of color images,the invisibility and robustness of the watermarking is considered,and the adaptability is improved by using the optimization algorithm in this thesis.The contents of this thesis are as follows:First,in order to solve the problem of poor robustness of spatial domain watermarking,the changes before and after the printing and scanning process of blue components of color images is analyzed in this thesis.Based on the derivation and verification experiments of the additive noise model of printing and scanning process,an approximate invariant of the blue component of color image before and after the printing and scanning process is found.The validity of the approximate invariant is proved by the experiments,and the method on digital watermarking technology of color image against print-scan attack based on the approximate invariant is proposed.Second,for make the algorithm have better invisibility and robustness,an algorithm on digital watermarking technology of color image against print-scan attack based on the approximate invariant is proposed in this thesis.Firstly,the classical pixel inversion model is analyzed and improved by combining the approximate invariant.And the pixel change model of color image is used to determine the embedding position of watermarking in the image block.Secondly,in order to protect the security of watermarking information,the carrier color image and original watermarking image are scrambled,and the scrambled times of two images are used as the key.Then,in order to enhance the watermarking capacity of the algorithm,an improved image segmentation method is used,and the watermarking is embedded by adjusting the number of pixels in the embedding part and the approximate invariant adjustment part.Finally,the experiments show that the algorithm not only has good watermarking invisibility,but also has good robustness against print-scan attack and various typical image attacks.Third,aiming at the problem that the adaptability embedding of the watermarking can't be realized due to the manual setting of the embedding strength,and the poor visual effect of the simple texture image with a high watermarking embedding intensity,an algorithm on digital watermarking technology of color image against print-scan attack based on the sparrow search algorithm is proposed in this thesis.Firstly,the problem of using pixel change model of color images with relatively simple texture and a large number of similar color backgrounds is analyzed.Secondly,the real printing and scanning process of color image is simulated mathematically,and the image effect is similar to the real print-scan attack by using multiple noise and other attacks.Then the sparrow search algorithm and the simulated print-scan attack are used to determine the best embedding position and embedding strength of the watermarking in the image block.Finally,the experiments confirmed the adaptability watermarking embedding for multiple color images is realized by the algorithm,the visual effect of simple texture images embedded with a watermarking is improved effectively.The algorithm is confirmed to have a good invisibility of watermarking and ability to against print-scan attack and various typical image attacks.