Document Image Watermarking Algorithm Based On Content Authentication

With the rapid development of the computer and Internet technology, the domestic corporation enterprise information deepening, the electronic documents are used widely in the enterprise intranet and in the E-government net, The digitalization of the Document paper facilitates the storage, processing and distribution of the documents information while enhances the efficiency and accuracy of information presentation. But the undesirable side effects are obvious: the electronic data's illegal distribution and the copy are easy, moreover the quality is not harmed. How to take the corresponding measure to protect author's copyright as well as the product information accuracy and the integrity becomes a most urgent duty. Digital watermarking, which originated from cryptography, provides a novel way for the protection of intellectual property rights, and becomes a hot spot in the research field of multimedia data security in recent years.Because of its own characteristics, it is easier for the document images to be copied and distribution, and in many cases, such as college entrance examination online marking and Medical electronic records, document images have a higher value than the natural images and video images etc. However, because the document image is not too much redundant information, in current society, the digital watermarking algorithm about document image is not so much. And the robustness are not good, the capacity of watermark embedding is small. This paper has conducted the research in view of the documents image's digital watermark technology.Firstly the research background and the present situation of digital watermarking are given, have analyzed the digital watermark basic principle and the correlation theories, enable the readers have a general understanding of the basic knowledge of digital watermarking. Then describe the image authentication watermarking system principles, the basic framework, features and so on, analysis the involved key technologies and the existing classical authentication algorithm in-depth, and points out the future direction of authentication watermarking.In this paper, after a detailed analysis of the characteristics of document images, we proposed a semi-fragile watermarking for content authentication of document image, which based on spatial domain, frequency domain features. In this algorithm, the watermark is generated based on the relationships of low frequency coefficient in DCT domain, which embedded watermark signals into matrix singular value larger data, Embedding algorithm use DCT transform, the watermark generation is relevant with the characteristics of the document image, which is a self-embedding watermarking algorithm, the watermarking system is blind and image authentication can be finished without exterior watermark. In the experimental phase, image with watermark has been attacked in several ways, such as JPEG compression and tampering. Experimental results indicated the effective of the algorithm. This watermarking is sightless, robust for conventional image processing, and fragile for images modification or tampering. Which be able to accurately detect tampering and can locate the tampered position.There are many incomplete problems of this algorithm. The according work will be done in the future. If the algorithm is also applicable to handwritten or printed document images which containing both characters in it with images need further verification. Document image is playing an increasingly important role as a special kind of image vector in current society. With the more and more research on document image watermarking, document image watermarking will have a bright future.