Research Of Image Watermarking Algorithm Of Robustness And Half Vulnerability Based On DCT

With the rapid development of information technology，making exchange andtransmission of digital works very fast and convenient. However，with the increasingpopularity of the Internet, brings people convenience at the same time, has initiatedmany problems, namely digital works of unauthorized use and malicious tamper.Therefore, how to effectively protect the copyright and content of the authenticationhas gradually attracted wide attention and attach great importance to people. at present,digital watermarking as a way, which can effectively resist digital image piracy andmalicious tampering, has been got a great deal of application. It has become a hottopic in the field of multimedia signal processing, but also an important subject in thefield of information security technology, images, as part of the multimediainformation, has an important role. in the research of copyright and the authenticationof content of works.This paper mainly studies the digital image watermarking technology, the mainwork has the following several aspects:First of all, The article summarizes and elaborates principle, framework,characteristics, classification method and evaluation standard of watermarking systemof the digital watermarking technology, and the paper also introduces in detailcharacteristic, principle, classification of robust watermark and Semi-fragilewatermark, and the difference between two kinds of watermark in the spatial andfrequency domain of classical algorithm.Secondly, this paper proposes an improved robust watermarking algorithm inDCT domain. This algorithm, which is on the basis of the original algorithm, nolonger simply choose low frequency coefficient or high frequency coefficient, butchoose the low frequency and the Intermediate frequency coefficient as a watermarkembedding position, which makes full use of low-frequency coefficient andIntermediate frequency coefficient of their respective characteristics, the algorithmbetter balance the contradictions between invisibility and robustness of the watermark.The experimental results prove that the method has better hidden performance, and can stand different levels of shear, JPEG compression, noise and median filteringattacks, and has good invisibility and robustness.Again, this paper proposes an improved image watermarking algorithm ofSemi-fragile in DCT domain. The algorithm not only guarantees image quality of thewatermark, but also can accurately positioning the position of image, which ismalicious modified, the experiment proved that, this algorithm has obviousvulnerability in the resistance of malicious modification, can more accuratelydetermine the content area of the image from manipulation At the same time thealgorithm does not affect the image manipulation positioning results for theconventional accidental modifications of the watermarked image, it realizes the imagecontent tamper with the alternative certification, and has good robustness andvulnerability.Finally, as an emerging technology，the digital watermarking technology,involving many disciplines and a variety of techniques, although it has been studiedfor years, but there are still many problems to be solved and the research that is notbeen touched in the area. at last, the paper sums up the digital watermarkingtechnology and makes an outlook to the development of digital watermarkingtechnology in the field.