Spread Spectrum Digital Watermarking Algorithm Base On Watson Model

The rapid development of computer and internet network technology has caused deep transform of human manufacturing, living and ideology. Human society has entered a new era of digital information. The characteristics of easy storage and easy transmission of the digital multimedia works has speed up the communication and transmission of knowledge and information. However, these characteristics are also double-edged sword which increasing pirate risk of digital multimedia information.Digital watermarking technology provides us with an efficient approach, which protect copyrights by embedding copyright information into the digital multimedia (figure, voice, and video etc.). Moreover, watermarking algorithm based on transform domain has strong robust, and can be combined with present image and video coding standard. As a result, watermarking algorithm has a great research value and application prospect.This thesis is about digital watermarking algorithm for static images. First we introduce the basic principle, models and algorithms of digital watermarking then it is focused on detailed research on discrete cosine transform(DCT) domain algorithm. A spread spectrum based watermarking algorithm is proposed based on Watson model, which calculate the just noticeable difference (JND) of sub-block image, then the frequency points insensitive to change are chosen and embedded to improve the robust. The extraction precision and performances of watermarking are improved. Simulation results by MATLAB software have verified the superior performances of the modified algorithm, especially under attacks of Gaussian white noise, salt and pepper noise, and JPEG compression noise by comparison to basis algorithm.