Blind Printing Based On The L ~ * A ~ * B ~ * Color Space Of The Wavelet Domain Watermarking

The digital watermarking realize the copyright through joining the marking information in the presswork,it provides an effective solution for the problem of presswork copyright.But most pictures come from printing and scanning such as the trademark, packing,books and periodicals,certificate,credential,stamp,magnetism card,the publication,the title page of video and music product,currency,bankbook,valued ticket, admission ticket,documentary evidencem,advertisement,calendar,name card,passport.In recent years,with the development of commodity economy,the pretended behavior followed and especially in printing presswork.People has researched methods on color printing pretends,but the cost increased on large scale.Digital watermarking is a effective method,and it does not increase the cost.Therefore,how to applies the digital watermarking in the printing presswork gradually becomes to an important topic.There has been many digital watermarking algorithms about pictures,but the key of digital watermarking is resisting PS-process(printing and scanning)attack.The article provide a new kind of digital watermarking algorithm.The watermark is embeded in the L~*a~*b~* color space,it could resist the A/D and D/A transform attack.First, author analyzed difference in the third level of DWT low frequency coefficient before and after PS process,and found that the relation of maximum and minimum value to the average value distance keep consistent,so we consider to express the bits of watermark with the consistent numerical characteristic;Before the watermark is embeded,we place in disorder the carrier and the watermark pictures with differert seeds in order to enhance the safety of the watermarking system.We can retracted the watermark without primitive and watermark pictures,it is a blind-watermarking algorithm.Finally,we do many experiments and prove that the algorithm can resist common attacks such as JPEG compressing, shearing,dirtying,revolves,adding noise,filtering,especially has good robustness in PS-process attack.The watermark extracted is clear and parameters could reach expected value.Thus we can use it to proof the copyright of presswork.The algorithm provides an effective method for digital watermarking applying in the protection of presswork copyright.