Document Image Transform Domain Robustness Of The Watermark

With the rapid advance of electronic technique and information industry, multimedia,Internet become a usual thing in people's daily life.Internet sweep the world, with the rapidadvance of multimedia technique and digital transfers, the use of digital media which in Internetand CD-ROM advanced quickly.Digital information process and net transfers can edit,amendand copy the original edition digital media absolute,in this way it make tremendous economyexpense for the author of the media, and meanwhile it's a challenge of the digital media'ssecurity, So it is become an important issue in intellectual property rights protection andinformation security that how to protect multimedia data from violation.At the beginning,the author of the media use cryptography, but cryptography only canprotect the media which in transmission,and when the media has been deciphered,thecryptography cannot protect it any longer.So,we need a new technique that can always protectthe media after it has been deciphered.As a main application of information hiding technique to multimedia field, the digitalwatermarking technique has been proposed as a new solution to the copyright protection. So inrecent years it has drawn extensive attention and has been widely researched and applied.Digital watermarking is involves image and speech processing, human audio and visualsystems, mathematics, computer network and application, communication, signal detection andevaluation and so on. It embeds some invisible information—watermark into the originalmultimedia data such as image, audio, video signals and so on, In this way it can authenticatethe ownership or integrality of these multimedia data so as to protect the copyright. Theembeded messages could be copyright information or other secret messages. Generally itdemands robustness, so that it cannot deleted from the media easyly.Even if the media has beendeciphered,compressed,A-D transform,the watermark can also hold in the media, so that it canalways protect the media.This article researched the use of digital watermarking in the copyright protection of image.First, it introduced the digitla watermarking technique and its background, classification,character, algorithm model and typical embed algorithm. Then give a introduction of humanvisual system and the use of matlab in digital watermarking. Give a introduction of the typicaltransform——Discrete Cosine Transform, summarize the characteristic of document image,base on this, a new watermarking algorithm for document image in DCT domain is proposed.This algorithm use the characteristic of the document image, embed two watermarks into theDCT coefficient, one watermark is used for sign the direction and the other is used for sign thecopyright, this watermarking algorithm have a strong robustness and can prevent the problem that watermark can not be checked which caused by rotate the image. In this article, a lot ofexperiments are conducted in order to test the robustness of the algorithm, the result indicatethat this algorithm is robust to the common image processing attacks such as filter, noisecontamination, JPEG compression, cropping, rotation and reversal.