Research Of Image Watermarking Algorithm Based On Discrete Cosine Transform

Digital watermarking is an effective method for protecting the copyright of digital products. The rapid development of Internet has both advantages and disadvantages. While one can acquire a wide range of multimedia data through the Internet, various problems (copyright violation, illegal copying, easy forging, etc.) arise naturally that can seriously harm the author's or the copyright owner's benefits. As the carrier of information, image, audio, and video are the main means of information communication. And as digital products, they include originators'work and wisdom. Thus their copyright, like the property right of the owners, should be respected and protected. How to protect multimedia data from violation has become an important issue in information security field. As one main application of information hiding technique to multimedia copyright protection, the digital watermarking technique, which embeds an invisible signal (watermark) to the original multimedia data (image, audio and video), has been proposed as a viable solution to the copyright protection and authentication of multimedia data in a networked environment since it makes it possible to identify the author, owner, distributor or authorized consumer of multimedia data. So it has drawn extensive attention in recent years and has been widely applicable. Digital watermark is a new direction in the information security field. It is a new technology which can protect copyright and authentication source.The author's personal copyright information can be embedded in the products.But we can't percept it,only special software can pick it up. This paper addresses the digital image watermarking techniques based on discrete cosine transform (DCT). First, an overall review is made on the digital watermarking techniques, including its background, general system structure, basic principle, state-of-the-art, and their application. Second, we analyze the current watermark developing status, after deeply analyzing the technical feature and request of DCT-based image watermarking technique, this paper discusses the influence of embedding watermark into different DCT frequency coefficients on watermark robustness and imperceptibility, such as DC components, the low and the high frequency of AC components. Finally, We propose a watermarking algorithm which combines an experimental selection of the DCT frequency coefficients with common edge detection technique.