Design And Implementation Of Color Image Digital Watermarking Algorithm Based On DCT

With the development of Internet and digital technology, the media and information transmission mode has been deeply changed. Since varieties of digital production are conveyed and published through the digital networks, it is urgent to solve the issues of security controller and copyright protection. Digital watermarking, which can overcome some uncontrollable issues for decrypting encrypted messages, has become a new information security area under this circumstance. It refers to a distinguished digital signal or mode, which is embedded in other data (host data) to prove its copyright.In recent years, digital watermarking technology has attracted a great deal of interest and concern, and has been widely studied and applied. Although much has been done on digital watermarking in the past few years, many problems remain to be resolved. In this article, a color digital watermarking algorithm based on discrete cosine transformation was introduced, in order to solve the problem of copyright protection of static color images. First of all, this paper introduced the research background of digital watermarking technology, the elementary knowledge, the classification, the application and the present research situation. Then analyzes the existing watermarking algorithms, in order to improving the robustness of watermark, the color image digital watermarking algorithm based on DCT is brought forward. Based on the space conversion performance of DCT, It achieved the goal of embedding and extracting watermark in color image. The watermark image was scrambled and adaptively embedded into the low frequency coefficients of image after DCT transformation, according to characteristics of the host image pixels. With the selected key while scrambling, the watermark can be extracted without original image. To test performance of the watermarking algorithm, a lot of experiments on invisibility and robustness have been done; experimental results show that the algorithm has good invisibility and strong robustness on common image processing operations, such as image cropping, free alteration, JPEG compression and scaling attacks, etc.Different from traditional spatial domain methods, the image watermarking algorithm brought forward in this paper has better robustness; And compared with the watermarking that based on binary image, it suits more to color image, thus has irreplaceable advantages; Furthermore, it achieved blind detection, for which extracted watermark is not required to provide the original image. It is consequently known to us that the method has certain value of theory and application, concerned with the request of robust watermarking, copyright protection and the experimental result, thus under the wish to bring some novel thoughts for development of image watermarking.