Research On Digital Watermarking Technique Of Static Image In Wavelet Domain

With the rapid development of the Internet, various kinds of digital multimedia information including text, image, audio and video etc. have widely distributed through network. But the information on Internet can be easily duplicated and modified. So the copyright infringing problem on Internet is becoming more and more serious. How to provide copyright protection has drawn extensive attention in recent years. To solve this problem, the digital watermarking technique has been investigated.Digital watermarking technique, which embeds special information into digital products, is a new method for copyright protection. With the help of digital watermark, we can prove the originator's owner to digital products that he creates, and the watermark can be the proof of authentication and prosecuting illegal copyright infringing.Basically, there are two common methods of digital watermarking technique: spatial domain methods and transform domain methods. Spatial domain techniques are easy ways to embed information, but they are highly vulnerable to even small cover modifications. In many cases even the small changes resulting out of lossy compression systems yield to total information loss.Transform domain methods hide watermark in significant areas of the host image that makes them more robust to attacks, such as compression, cropping, and some other image processing, than the spatial methods. However, while they are more robust to various kinds of signal processing, they remain imperceptible to the human sensory system. There are two main transform domain methods, one is to use the discrete cosine transformation (DCT) ; the other would be the use of discrete wavelet transforms (DWT).In this paper, we main discuss the digital watermarking algorithms in wavelet domain. Wavelet analysis is internationally recognized up to the minute tools for analyzing the time-frequency. It has higher robustness to embed digital watermark in wavelet coefficients. A non-blind digital watermarking algorithm is proposed in this paper. The positions of embedding watermark are decided according to human visual system and the image itself. Experimental results show that the watermark is perceptually invisible and the proposed scheme is robust to various image processing operations. Then the method is improved based on the relationship of image wavelet coefficients and statistical characteristic of theimage. The method processes the watermark as a binary image and classifies the wavelet coefficients into two groups using JND (Just Noticeable Distortion) . The watermark is embedded in different way respective to the class. The host image is not required for watermark detection. In the end, the paper introduced a digital watermarking method in regions of interest (ROI) , so special region does receive better protection.