Digital Watermarking Algorithm Based On The Fractional Fourier Domain Image Features

Digital watermarking technique, a new method for copyright protection, has become one of the hotspot techniques in the multimedia information security field. At present, the algorithm researched is mainly in the transform domain,such as DCT and DWT. The Fractional Fourier reansform(FRFT)is a new tool for time-frequency analysis,which has some excellent properties for the some time-verity signal. The FRFT is more and more favoutited by the signal processing researchers after the fast algorithm is put forward. This dissertation is supported by the subject of the National Natural Science Foundation of China (No.60472044): " The theory and application of image digital watermarking based on fractional Foutier transform". On the basis of chirp-typed digital watermark algorithm reaearched, this paper focuses on both the random sequence and the two-value image watermarking algorithm which based on fractional Fourier transform. The main content and contributions are:1. The erengy distribution, the information contained in the amplitude and phase, real pary and imge part of the image at different fractional Fourier transform have analysis and verified by simulations. The simulations show that all of the porpertities present above of an image will different along with the vatity of the transform angle. This comclusions gives the reference for choosing the best transform angle and the position for the wantermarking algorithm..2. Using the characteristic of the coefficient of the FRFT, the random sequence watermarking based on fractional Fourier transform is proposed, and the watermarking capacity and how to choose the angle is disschssed.The simulation results have shown that the algorithm is robust to gaussian noise,salt noise and ropping attacking in a certain extent. Compared with the watermarking in DCT, the transform angle of the FRFT adds two keys so that the security is better.3. When the reansform angle is lager, the amplitude part of the FRFT of an image just influences the background of the original image. With this, a two-value image watermarking scheme in amplitude of the fractional Fourier transform is proposed in this paper. The simulation results shows that this algorithm is robust to the common image processing, suah as noise, JPEG etc.