Research On Digital Image Watermarking Technology

Digital watermarking, as an important branch of data hiding technology, is a research hotspot in the multimedia information security field, among them, the digital image watermarking technology received the most extensive study. Firstly, the basic concepts of digital watermarking and the basic principle, typical algorithm, and system evaluation of image watermarking are introduced in the paper; Secondly, the bicepstrum theory foundation is introduced, the bicepstrum image watermarking algorithm proposed by the author is simulated in computer; Finally, a novel image scrambling matrix is proposed.Cepstrum transform which is a non-linear transform proposed in the early 1960s, has a widespread application in the voice signal processing. The bicepstrum is defined as cepstrum of bispectrum, also belongs to the high order cepstrum. A watermarking algorithm in bicepstrum domain is proposed in the paper, which can be used to traitor tracing. A binary random sequence as a watermark is embedded into the phases of bicepstrum coefficients of an image. Experimental results show that the watermark is Transparent, and it is robust to common digital signal operation and some attacks, such as noise, cropping , rotating, median value filtering and JPEG compression.Digital image scrambling technology can be used to the pretreatment of the digital image watermarking, because it can improve the safety and robustness of watermarking system. The image scrambling matrix W that the author studies has the same characteristics of easy coding and decoding with Arnold matrix, they are also periodicity. First, the thesis presents the W matrix conformation method; Then it proves that the W-based transform possesses periodicity, also extensive computations are made; Finally, a simple DCT image watermarking algorithm is selected by the author to test the actual effect in the watermarking system. The results show that: when the module parameter is integral power of two, the period of W matrix is bigger than Arnold matrix, so it is safe enough in the image encryption procession. Moreover, when the watermarking image scrambled with W matrix is embedded into the source image, it has good transparency, also it is well robust to common digital signal operation.