Digital Image Watermarking Algorithm Based On Chaos

Digital watermarking technology makes it possible to solve the problems, which are about copyright ownership and identification of multimedia products. With certain algorithms embeds markings into multimedia products, which include image, audio, video and so on. The marks may embed into multimedia with certain algorithm. The marks can be pseudorandom sequences, binary images, whether they have meaning or not. When identifying, the watermark is detected or extracted through certain algorithm by computer.The features of chaotic system are fine pseudorandom characteristics, sensitivity dependency to original value and control parameters. And it is now extensively used in communication system, encryption and so on.In this thesis, firstly, classical algorithm in spatial domain is analyzed. The algorithm in spatial domain is single, and the embedding watermark's capacity is large. But the disadvantage is pour robustness. To improve the robustness of the algorithm, chaotic system is added. Simulation results show that the safety and the robustness of watermark are enhanced.Secondly, block DCT algorithm based on chaos is proposed. The algorithm in frequency domain has good robustness, but with small capacity.Lastly, combining the advantages in algorithms of spatial domain and frequency domain, a new algorithm in combinational domain based on chaotic system is proposed. The watermark information is divided into important part and unimportant part, with whatever you want to. The important is embedded into frequency domain, which has good robustness. The unimportant with large capacity, is embedded into spatial domain. Extracting watermark, there is no need of original information.Simulation results show that under the no attack situation the extracted watermark is very well. Attack the watermarked image through adding noise, filter, and JPEG compress. In the extracted watermark from the attacked image, the important part, which is embedded into frequency domain, has good robustness. That is to say, under safe situation, the algorithm increases the capacity of watermark. By attacked situation, the important part is saved for identification.