Digital Watermarking Algorithm Based On Transform Domain And HVS

The rapid development of the Internet, multimedia and communications technology, multimedia transmission and reproduction of digital products is very easy, which makes that the security of multimedia data has been paid more and more attention. Digital watermarking technology is a new method which is to solve the problem of multimedia data security, and has become a hot issue of information security field. This thesis analyzes and studies the results on the basis of domestic and foreign, has mainly studied transformation domain digital image robust watermarking. The major works involved are as follows:1. According to the illumination of the image masking and texture masking properties with human visual system, an improved adaptive image watermarking algorithm for grayscale on DCT is proposed. Illumination characteristics of the image reflected in the brightness of the image background. The algorithm selects the block that is larger brightness and texture as the watermarking embedding point. When the watermarking is embedded, embedding strength can be adjusted adaptively. Simulation experiment demonstrates that the algorithm can resist common image processing operations. Robustness and transparency are very good. It is a robust watermarking algorithm.2. The thesis proposed a watermarking algorithm for color images on DWT by analyzing the principles of human vision system and the characteristics of JND system model. It considers the green component and blue component characteristics of original color image. First, green and blue components are transformed in discrete wavelet transformation. Second, watermarking image is encrypted through chaotic system. Last, watermarking sequence is embedded in the larger JND values corresponding to low frequency coefficients of green and blue components, which is able to achieve blind extraction and is a robust watermarking algorithm. Experimental result demonstrates that the algorithm is highly robust to a common image processing operations, which is a robust watermarking algorithm.3. According to the human visual system model of Contourlet domain and the characteristics of Contourlet transformation, a color image watermarking algorithm on Contourlet transformation is proposed. First of all, the green component of color image is transformed in Contourlet transformation, and then algorithm selected the larger values of the human visual system masking corresponding to coefficient as watermarking embedding points in the maximum energy subband. When watermarking is embedded, it is modified coefficients by the parity quantization. When watermarking is detected, it is able to achieve blind extracted successfully. Experimental result shows that the algorithm has good performance and can achieve blind extraction.The presented robust frequency-domain digital watermarking algorithm has very good robustness and transparency, which is very important significance for copyright protection, acts of piracy,etc.