Research On Digital Image Watermarking Algorithms Against Geometric Attacks

The digital watermarking technology is an important means of copyrightprotection, the official institutions started early extensive research and application.The specific markers or secret information is embedded in various digital media, suchas, the audio, video, or image, etc. through the digital watermarking technology. It canbe used to protect the copyright or identify whether these digital media for copyrightprotection is edited.Firstly, this paper introduces the development history, main characteristics,classification method, relevant application field and some existing digitalwatermarking algorithms of digital watermarking technology simply, and describessome common watermark attack methods, summarizes the relevant evaluationstandard and the current technical difficulties. Second, further study the relevanttheories of each algorithm and typical digital watermark algorithms. Combining withthe existing watermarking algorithms, two kinds of watermarking algorithm isproposed that aimed at the difficulties in the current digital watermarking in resistanceto geometric attacks, one is the domain digital watermarking algorithm applied tocolor images hypercomplex Fourier transform to resist geometric attacks and anotheris the gray image watermarking algorithm based on lifting wavelet transform to resistgeometric attacks. The first algorithm performs zigzag sorting and CDMA spreadspectrum to the watermark image, so that we can improve the invisibility ofwatermark information, and then spread spectrum watermark image and color imageafter four yuan hypercomplex Fourier spectrum coefficient is divided into four part,respectively, and combining with method of uniform log-polar mapping to embed thewatermark information specified into the carrier image spectrum coefficient by setting the related parameter, then extract the watermark information from the differentattacked watermarked images respectively, finally, compare and analyze with theoriginal image were. The watermark generation process of second algorithm is similarto the prior, the lifting wavelet transform is used for processing the carrier imageduring the watermark embedding processing. The differences from the first generationwavelet is integer transform used in the process of transformation, and the transformcompletely will not affect the accurate reconstruction, then extract the watermarkinformation from the different attacked watermarked images respectively, finally,compare and analyze with the original image were. At the same time, this paper alsoproposes a rotation Angle estimation algorithm based on Fourier logarithmictransform, this algorithm has the characteristic of high precision, small amount ofcalculation. Algorithm in this paper and compared with the existing algorithms, thesimulation results shows the watermarking algorithm has higher robustness andinvisibility, and has increased performance in resistance to geometric attacks.