Research On Digital Watermarking Algorithm Against Print-scan Attack

With the continuous development of multimedia technology,data transmission is becoming more convenient,which has caused many problems of infringement,malicious attacks and piracy.Digital watermarking technology is particularly important in copyright protection.Although electronic documents have gradually replaced paper documents,there are still many important documents such as documents,certificates,books and other products that need to be printed,and the watermark anti-print scanning attack ability is also very important in copyright protection.Currently,Many scholars have chosen watermark embedding in a frequency transformation domain with less visibility.However,the relationship between the watermark concealment,robustness and embedding capacity,In this paper on existing frequency domain transformation methods,Select the two frequency domain decomposition methods of DWT,non-sampling Contourlet transform(NSCT),Combined with the watermark disorder method and the singular value decomposition(SVD),Improve the anti-printing scanning ability of the digital watermark.The main studies of this subject are as follows:1?By analyzing the advantages of DWT transformation in image decomposition,an anti-print scanning digital watermark algorithm based on DWT and SVD is proposed.It analyzes the influence of printing scanning on DWT decomposition series and subband coefficient and the advantages of SVD,the watermark is low frequency subband of secondary DWT decomposition,and the feasibility of the embedding position is verified.The feasibility of the algorithm is verified by simulation attack as well as print scanning attack test.2?In order to solve the problem of watermark embedding capacity and realize the blind extraction of watermark,an anti-printing scanning blind watermark algorithm based on NSCT and SVD is proposed,which first performs three-stage NSCT transformation of the carrier image,selects low-frequency sub-band according to the watermark size,matches the watermark size,performs SVD decomposition,selects the maximum element to modify according to certain rules,so that without the participation of the original carrier image in the extraction process,to realize the blind extraction of watermark.Moreover,the advantage of non-downsampling by NSCT decomposition expands the embedding amount of the watermark.3?In order to realize anti-print scanning attack digital watermark for color image,a digital watermark algorithm in CIEL*a*b* color space is proposed,converting the RGB color space of color image into CIEL*a*b* before performing watermark embedding.The proposed algorithm combines the advantages of the first two algorithms to directly superposition the watermark on the singular value matrix kter the NSCT transformation,and realize the robust watermark facing the color image while increasing the watermark embedding capacity.In this paper,two kinds of anti-print scanning digital watermarking algorithms for grayscale image and one for color image are proposed.The experimental results show that the anti-print scanning ability of the algorithm is satisfactory.