The Research On Digital Watermarking Technology For Medical Image Based On Active Code

With the rapid development of medical imaging technology,medical image has become an important basis for doctors to diagnose the patient's condition,and plays an important role in the medical field.However,medical image is vulnerable to be attacked or malicious tampered in the actual transmission process.Thus,the copyright protection problem caused by it has been paid more and more attention.Digital watermarking is an important technology which is to determine the ownership of copyright and to judge whether the image has been attacked.It can provide authenticity and integrity for medical images.In this thesis,based on features and advantages of the existing watermark algorithms,we propose two digital watermarking algorithms which are suitable for medical images and have super-large capacity and strong robustness.The main contents are as follows:1.In order to solve the low embedding capacity problems of digital watermarking,in this thesis we present a new information hiding method using active code features of storing information in the cloud.Firstly,the information is embeded into the active code.Then the active code is embeded into the medical image.Eventually,this way can greatly increase embedding capacity of digital watermarking.2.For gray-scale medical image,digital watermarking algorithm based on active code and DWT-SVD is proposed in this thesis.First,the embedded watermark information is used to create the encrypted active code.Next,the medical image is decomposed by secondary discrete wavelet transform and we select the low frequency part block,and choose each block appropriate point into a new matrix.Then,the new matrix is singular value decomposition.Finally,the active code is embeded into s-matrix of singular value decomposition.The experiment results showed that the digital watermarking algorithm not only has super-large embedded capacity,but also has good invisibility and robustness against wide range of attacks such as rotation,noise,cropping and filtering attacks.3.For the widely used color medical image,digital watermarking algorithm based on active code and DCT-DWT-SVD is proposed in this thesis.First,the R,G and B channels are separated for color medical images.Then,on the basis of the proposed DWT-SVD algorithm,the algorithm presented in this thesis combines with the energy concentration characteristics of the 2-level DCT and z-shape scanning,and we select the appropriate embedding stra tegy to design the watermarking system.The simulation results showed that the algorithm not only meets the specific requirements for visual quality of medical image,but also has strong robustness to the processing of color medical image.