The Robustness And Weakness Of Printing With Halftone Watermark Image

At present, for protect the digital product from destroying and interpolating illegally, we used the robust watermark to defend the safeness of copyright, used the weak watermark to defend the completeness of the digital product. This paper principally discussed a method to produce a multifunctional watermark, which would oppose the interfering just like cutting, creasing and image two-valued that could affect the watermark in the carrier image.In order to make the watermark have multifunctional effect, in other words, in order to extract the watermark when the carrier image had been attacked, and also for checking the completion of the message from the carrier image, this paper used the transformation in wavelets domain, which would generate frequency component. This idea consulted the method that implant watermark into the image which used multi-channel filter bank, in detail, getting the image across multi-channel filter bank in latitudinal and longitudinal row to get the different frequency component, and then got the different usefulness watermark into the corresponded frequency component. According to the characteristic of human eyes when we observed things, on the assumption that the carrier image had been attacked by the same level, the watermark which implanted in the low frequency had the robust ability to resist the attacked, the watermark which implanted in the high frequency was easy to verify the completion of the original image.The method that implanted the watermark into the carrier image was according to comparing the coefficient of the frequency domain after wavelet transform. The watermark finally implanted into the carrier image in this paper was two-valued image, and the message of that image was consist with"0","1", which could suspect one-dimensional-array on the emulation program. Implanting the watermark was basis of the logical relationship that put the carrier image into piece on line to transform into the wavelets domain. This process had been going twice, in other words, implanting double watermark.For better robustness of the watermark, to extract legible watermark from the carrier image that was attacked, the position that the watermark implanted selected the low frequency after wavelets transform of the carrier image, and the strength was strong. The result of emulation program showed that the watermark by this way could was effectively resisted the aggression just like cutting and creasing. The extracted watermark was easy to recognize when the carrier image had been threshold and the message of the image had been lost.For better weakness of the watermark, to check the completion of the image, the position that the watermark implanted selected the high frequency after wavelets transform of the carrier image, and the strength was weak. The result of emulation program showed that the watermark by this way could be weak and then it also was identifiable when the image was destroyed by cutting and creasing. When the carrier image was two-valued, the weakness of the watermark was prominent.This paper has discussed the multifunctional watermark, which was not only robustness but also weakness in the same digital objective. It's implanted double watermark so that we could extract different watermark by different usefulness.