Robust zero-watermarking algorithm against dual print-and-scan based on direct coefficient comparison
A technology of secondary printing and DC coefficient, applied in the fields of information security and document anti-counterfeiting, can solve the problems of signal processing attacks, etc., and achieve the effect of strong resistance to secondary printing-scanning ability
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[0055] 1 Influence of print-scan on the relationship between the DC coefficient values of two adjacent sub-blocks in the wavelet low-frequency approximation sub-band
[0056] Taking Baboon, a 512×512 256-gray-level image, as an example, the influence of a print-scan on the value relationship of the DC coefficients of two adjacent sub-blocks is investigated. image 3 and Figure 4 They are the original Baboon image and the Baboon image after one print-scan and post-processing. The three-level harr wavelet base DWT is performed on the image, and the low-frequency approximation sub-band is divided into 4×4 sub-blocks that do not overlap each other, and DC coefficients are generated by DCT for each sub-block.
[0057] Figure 5 is the sign distribution of the difference between the DC coefficients of two adjacent sub-blocks in the original Baboon image wavelet low-frequency approximation sub-band, Figure 6 It is the positive and negative sign distribution of the DC coefficie...
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