Blind Digital Image Watermarking Technique Based On Wavelet Analysis Study

In recent years, access to multimedia data has become much easier due to the rapid growth of the Internet. While this is usually considered an improvement of everyday life, it also makes unauthorized copying and distributing of multimedia data much easier, therefore presenting a challenge in the field of copyright protection. Digital watermarking, which is inserting copyright information into the data, has been proposed to solve the problem.As an important branch of information hiding, we analyzed the current watermark developing status, basic characters and problems of digital watermark technology, and discuss the general frame of digital watermark processing system . The algorithm in frequency-domain is relatively robust, compared with the one in spatial-domain. In this dissertation, firstly, we studied wavelet transform and some wavelet-based watermarking algorithm in detail. And then we present a novel wavelet-based watermarking algorithm, in which the binary digital watermark is embedded by changing information of some bit planes in DWT subimages at different resolutions. The watermark can be extracted without the host image. Experimental results and analysis are then given to demonstrate that the proposed algorithm is effective with good perceptual invisibility and robustness and can resist various processing operations.Secondly, we present a blind watermarking scheme for robust spatial-domain digital image in the paper. The pixels of the binary watermark image are pseudo-randomly permuted to form a new watermark image. And they are embedded in bigger contrast regions of image by a quantization strategy. The scheme is adapted to various texture images and can extract the watermark without the original image.Besides, We also proposed another effective scheme to embedded watermark in digital image. We embed the watermark into the middle frequency bands of the DCT coefficients of the original image by comparing the selected coefficients. The proposed technique could actually survive after several kinds of image processing, supporting good perceptual invisibility and robustness.