Research On Digital Watermarking Of Still Images Based On The Technique Of Split Blocks

With the fast development of internet and multimedia, how to protect the information of multimedia and digital products has already been an important issue cared by all the countries in the world. Digital watermarking occurred in such a background, which can make up for the shortcomings of traditional methods of information cryptology. Digital watermarking has widely used fields in authentication, counter-counterfeiting, counter-tampering, safety and integrity of data, so it has triggered a great care from people. Nowadays the digital watermarking is developing quite quickly, and a lot of scholarly achievements have been obtained.Research on theories and methods of digital watermarking in the fields of still images has been made in this dissertation. Firstly, the concept of information hiding and digital watermarking has been introduced, and the basic frame of digital watermarking has been explained from the five fields of generating, embedding, extracting, detecting and attacking. The classifications, characteristics, typical algorithms and utilized fields of digital watermarking also have been simply introduced. Based on characteristics of human visual system, two methods used for classifying the blocks of images are proposed and compared. Then based on visual perception characteristics of color images, the blocks of color images are classified so that robust watermarking can be embedded. A visible watermarking algorithm based on methods of classification of blocks is proposed, which can maintain the quality of original images and make the details of watermarking visible after the watermarking is embedded. Two fragile watermarking algorithms are proposed for detecting the attacks against the watermarked image by visible watermarking. At last, a reversible and fragile algorithm is designed, by which the watermarking can be reversed and the tampering can be localized.