Research Of Digital Image Watermarking Algorithms

With the rapid development of the information technology and the network applications, copyright authentication and network security technology is facing great challenge. Digital watermarking technology is an effective method to solve the problem described above, and the technology was researched deeply and applied widely.The research background, current situation and development trend of digital watermarking technology were described. The principles, characteristics, classification, basic framework, typical method, common assault and evaluation criteria of digital watermarking technology were analyzed. Based on the above basal theoretical research, combined with discrete cosine transform, chaos theory, singular value decomposition theory. Two digital image watermarking algorithms were proposed in this paper.(1)The barcode printing watermarking algorithm based on DCT domain. The printed counterfeiting algorithm based on the printed counterfeiting technology was proposed, the binary barcode was regarded as the watermarking information in this algorithm. The advantage of this algorithm is that the watermarking is robust to the first PS (print and scan) and fragile to the second PS. At first, encrypting the watermarking information with chaotic method and the information can be initial hidden initially. Then, implementing the blocked DCT transform of the embedded watermarking image according to the size of the watermarking image. Selecting the low frequency coefficient and embedding the watermark information by modifying the coefficient of amplitude and plus-minus sign. During the watermarking extraction process, implementing the blocked DCT transform of the watermarked image at first, and then extracting the watermarking information according to the plus-minus sign of the DCT coefficients. The modifying extent is smaller and the algorithm has good invisibility. The watermarking was extracted according to plus-minus sign of the DCT coefficients, and the process is blind extraction. The simulation experiment results show that the algorithm has good invisibility, and the design of the algorithm accords with the requirement of the printed counterfeiting technology.(2)The digital watermarking algorithm based on DCT and SVD. The chaos technology was pulled into the algorithm. Firstly, encrypting the original watermarking image with the chaos technology. The watermarking information can't be extracted if the chaos initial value is unknown, because the similarity of the encrypted watermarking and the original watermarking is low. Then, transforming the carrier image for block DCT, sorting the DCT coefficients according to Zig-Zag order and selecting the low frequency coefficients to constitute a coefficient matrix. Transforming the coefficient matrix with the Singular Value Decomposition method and embedding watermarking to the S component. The resist ability is improved in this algorithm. The SVD's U and V components produced during the embedding process should be used when extracting the watermarking. Simulation results show that the algorithm has good invisibility, while is better robust to the common attacks.