Research On Image Watermarking Based On DCT

With the development of modem computer's computation capability , popularization of computers and the quick development of Internet, these security of personal information is being threatened. Traditional data encryption can partly prevent invalid distribution of data, but with the development of decryptin technology, almost all the encrypted data are facing the danger of being cracked. Many hackers cannot help trying to crack the encrypted data while finding them,which makes the encrypted data are as dangerous as the unencrypted. In addition to that, when it comes to the validation and ownership check of data in use, traditional encryption c an not help anymore.On the other hand,With the rapid development of Internet and multimedia technology,digital watermarking is developed for the applications of digital multimedia, such as copyright protection,image authentication,and proofof ownership.In this paper,we firstly introduce the background of digital watermarking,main algorithms, and properties.Then image watermarking techniques and visible wateremark are described.After that , image watermarking based LSB are described. and then, we introduced the basic principle of DCT watermarking,the DCT used in JPEG, DCT-based watermarking technology , DCT attacks on the watermark and Capacity Analysis of DCT watermark.At last,we give a new watermarking algorithm based on DCT presented. The Watermark of DCT-based adaptived with signal-to-noise ratio .