| With the sharp increase of Internet users and the fast development of the technology of multimedia,the digital production has been more and more popular. It has become urgent that how to proect the copyright of digital production and prevent the pirate of the digital production because it is much easer to transmit,copy,tamper and pirate the digital production.Digital waterwatermarking emerges as the times require and becomes a hot spot in the research field of multimedia data security in recent years.After those digital watermarking technologies, including digital watermarking based on wavelet transform and digital watermarking based on fractal encoding and digital watermarking based on both them, are studied, those following public watermarking algorithems are presented.Firstly, considering the features of human visual system(HVS) and wavelet transform,a adaptive watermarking algorithm is proposed.lt adopts fast integer wavelet transform;each watermartk bit is embedded into every cooeficient of one wavelet tree of host image.Quantization step of each coefficient is automatically computed in terms of the JND to adaptively embed watermarking.Secondly, a digital watermarking approach based on fractal coding is designed ,it can be completed by changing fractal coding parameters.It adopts fast fractal image coding in order to reduce time of fractal coding.Chaos sequence is used to encrypt watermarking to enhance the security of watermarking systemFinally ,a new algrithm based on fractal image coding and discrete wavelet transform is proposed and can adaptively select locatlity to embed digital watermark in term of the HVS and fractal image codeing error to get best quality for image with watermarking and enhance the security of watermarking system.All experiment data is drawn out for the performance analyses. The experimental results show that the imperceptibility and robustness of the last method can be guaranteed and its synthetic performance is better than those former methods. |
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