The Study On Algrithms Of Still Image Watermarking

Digital watermarking has recently been proposed as a new means to provide copyright protection of multimedia data and image authentication. Discrete Cosine Transform and Wavelets are respectively the key technique in the source compression coding Standard JPEG and source compression Standard JPEG-2000, the applications of digital watermarking in still images are systematically discussed .Two robust watermark schemes based on DCT domain and DWT domain are given separately, so is the scheme of digital watermarking of text based on pixel change of words block of lines.Based on the wavelet transform,this thesis put forward a spread spectrum digital image watermarking algorithm,in which m-sequences are applied to the structure design of watermark. Experiment results indicating the schemes are robust to JPEG compression and noise.Along with penertrated analyse of the throry of genetic algorithms(GA),an innovative watermarking scheme on genetic algorithms in the DCT domain is proposed. Computer simulation indicates this scheme can find an optimized DCT domain frequence bands when we embed an watermarking image into an digital iamge.Simulation results prove the balance of conflicting between the invisbility and robustness.In addition to the robusteness of the proposed algorithm, we also improve the watermarked image quality with the aid of GA.Attacking experiment results reveal the fact that the scheme is robust to JPEG compression, noise and image-cropping.Finally,a watermarking method for text documents is presented by means of pixel change of words block.The watermark is embedded into documents in the light of its line characteristic. Simulation results show that this method ,to some extent ,is robust to the typical image processing attacks such as JPEG compression, iamge_cropping and noise.In this paper shuffling techniques has been studied in the application of digital watermarking.Shuffling techniques can disperse the distributing of error bits ,which could improve the watermarking robust.This experimental result indicate that these techniques are very effective in keeping resilience to cropping attack.