A Robust Digital Watermarking Algorithms Research

With the development of Internet and multimedia processing technique,media can be conveniently expressed, storaged, obtained and distributed in the form of digital. However, digital media can be copied and transmitted with the low cost and high speed, coping and processing digital media nonlicetly is easy. So the protection of copyright becomes a serious problem. Digital watermarking technique is an important method of protecting copyright. In this paper, a digital image as the research object, the image of the transform domain to embed watermark in order to improve the robustness and invisibility, but simply based on wavelet transform and Contourlet transform watermarking algorithm is difficult to resist filtering, shear and other attacks. So this paper uses quantization algorithm ideas to embed watermark, enabling robustness and invisibility reach a good compromise and also achieve blind watermark extraction.A new blind watermarking algorithm based on the quantization of mean value in wavelet domain is proposed. The original image is decomposed by using discrete wavelet Transform. According to the characteristics of Human Visual system(HVS),insensitive to the image's texture and edges. Then the vertical and horizontal high frequency band are chosen and divided into non-over-lop blocks, watermark is embedded into the larger mean value blocks embedded into. According to the blocks'mean value modification amount, update all blocks'coefficients with the same modification amount as the mean value, then complementing embedded into watermark. The watermark can be extracted without original image. It is truly blind watermark algorithm, and the extracting needs the author's keys, which improve the watermarking security . The experiments show that the proposed scheme has a good imperceptibility and high robustness to various common image processing attacks such as added noise, JPEG compression, cropping and filtering.This paper presents based on neighboring mean value relation quantization watermarking scheme in Contourlet transform domain. After the Contourlet transform, the original image was decomposed into series of multi scale, local, and directional subimages , the original watermarking was scrambled by Arnold transform, and choose the larger energy high frequency as embedded domain. The embedded positions are chosen according to the mean value of neighboring symbol and coefficient relation. Then the embedded positions coefficients are modified by quantization scheme. The retrieving watermarking scheme is a blind detecting process, and it does not need original image. The experiment results show that this watermark scheme is good invisible and strongly robust to watermark attacks such as noise adding, JPEG compression, filter, and cropping.