Array Stochastic Resonance Theory Research In Digital Image Watermarking

Today,the copyright protection of digital products and certification of the integrity problem are important and attractive.Since the 20th century,digital watermarking technology has been attracted attentions in the world,and also yielded many significant results.However,as a new area of research,there are still a lot of digital watermarking technology theories and technical problems to be solved. Therefore,this thesis focuses on the field of digital watermarking,and the applications of nonlinear system to digital watermarking detection under various attacks.Firstly,we propose an approach of the digital image watermarking algorithm based on stochastic resonance.The watermark information is the binary pulse amplitude modulated signal,and then replace the selected DCT coefficients of image with the embedded one.We use a nonlinear bistable detector to detect the watermark.This kind of non-linear detector is robust to the delayed signal detection,and can extract the watermark well.In addition,we also experiment with an array of bistable systems, to further improve the above method.The experimental results show that bistable arrays have a more robust performance in attacks,such as JPEG compression and shear.We also consider another saturating dynamical detector with good detectability in various attacks.Furthermore,we re-embedded watermark through the coding way,and the watermark coed by this watermarking algorithm is embed into the host image.We compared a single bistable detector's test results with the result of a parallel array of bistable detectors.The merit of array stochastic resonance in digital watermarking is obvious.Finally,this application of nonlinear systems to DCT domain watermarking detection indicates that nonlinear systems are potential signal processors,and the extended stochastic resonance is a useful mechanism that deserves to be further studied in digital watermarking field.