| In recent years,Citizens'awareness of copyright protection has increased significantly.The anti-counterfeiting technology based on amplitude modulation screening arises at the moment,which is the reliable guarantee of digital property.Because of Its production process is relatively simple and low cost,it has been widely used.The technology facing two questions,first,there are a lot of redundant calculations in the algorithm of the amplitude modulation screening,resulting in wasted time cost;Second,the result of extracting anti-counterfeiting information is not clear,which can't meet the standard of secondary utilization.Based on the above problems,this thesis focuses on AM screening,grating anti-counterfeiting and anti-counterfeiting information extraction.The main work of this thesis is summarized as follows:1.The thesis deeply studies related parameters of AM screening and the growth rule of dot;analyzes the relationship between the minimum threshold matrix and mesh unit under different screening angles;demonstrates the equivalence of the minimum threshold matrix and mesh unit threshold matrix and the conversion relationship between them,which provides a theoretical basis for the design of cell threshold matrix.2.Aiming at the problem that the time complexity of AM screening algorithm based on minimum threshold matrix is high,this thesis studies the algorithm deeply,summarizes the law between minimum threshold matrix and cells,and proposes an AM screening algorithm based on cell threshold matrix,which can avoid repeated calculation.The algorithm reduces the time complexity of am screening from((2)to(1).According to the close relationship between AM screening and grating anti-counterfeiting,two kinds of grating anti-counterfeiting technologies,phase modulation latent image method and master variable angle latent image method,are realized by cell threshold matrix AM screening.The experimental results show that the AM screening algorithm based on cell threshold matrix can effectively avoid the problem of repeated calculation,and the screening speed is significantly improved compared with the minimum threshold matrix.3.In order to meet the needs of fast detection of screening angle of each channel when extracting anti-counterfeiting information,an algorithm based on local halftone image to calculate screening angle is proposed.The time complexity of the algorithm is(~2),and the screening angle is calculated from the local halftone image by counting the connected area of the dot.The accuracy of the algorithm is 99.75%.4.In order to solve the problem that the result of extraction is not clear enough or even can not be extracted,an information extraction algorithm based on cell threshold matrix is proposed.The algorithm takes cell as the basic operation unit,compares the cell with the pre stored cell information in hash structure,and can judge whether the cell hides anti-counterfeiting information with(1)time complexity,and the accuracy of anti-counterfeiting information extraction can reach 99.43%.Compared with the traditional detection results based on grating,the visual recognition of the results extracted by this algorithm has been greatly improved.5.In order to verify the feasibility of grating anti-counterfeiting technology based on cell threshold matrix,linear grating and point grating based on minimum threshold matrix are designed for hidden information extraction.In the experiment,the hidden effect of grating shows that the grating anti-counterfeiting based on cell threshold matrix has the ability of hiding anti-counterfeiting information.Based on the technology and scheme studied,a software system of information hiding and information extraction based on AM screening is designed.The system integrates the functions of AM screening based on cell threshold matrix,grating anti-counterfeiting and anti-counterfeiting information extraction,which are proposed in this thesis.The system can be applied to the protection of digital image intellectual property rights. |
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