6762

6304

كارشناسي ارشد

هوش مصنوعي

اصفهان: دانشگاه صنعتي اصفهان، دانشكده برق و كامپيوتر

1390

ده، [92]ص.: مصور، جدول

ص.ع.به فارسي و انگليسي

شادرخ سماوي

22/3/91

محمدرضا احمدزاده، بهزاد نظري

1396/09/14

كتابنامه

برق و كامپيوتر

مهندسي برق و كامپيوتر

ID6304

به فارسي و انگليسي: قابل رويت در نسخه ديجيتالي

93 Watermarking in Contourlet Coefficients Using Genetic Algorithm Hoda Rezaee Kaviani h rezaeekaviani@ec iut ac ir Date of Submission 2012 03 05 Department of Electrical and Computer Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisor S Samavi Prof samavi96@cc iut ac irAbstract Due to extension of computer networks and Internet digital contents can nowadays be easilyexchanged As a result many copyrighted contents may be shared illegally and this has concernedmultimedia owners To overcome this problem watermarking schemes are proposed to protectcopyright of digital contents such as digital images These techniques are divided into two groupsof spatial and frequency domain methods A proper watermarking scheme must have highrobustness as well as preserving visual quality of the watermarked image Since that robustness andfidelity are in contrast to each other having these features at the same time is a major advantage fora robust watermarking method In this thesis after discussing watermarking concepts andintroducing different types of watermarks attacks and several watermarking methods fourwatermarking algorithms are proposed Since proposing a robust watermarking method for digitalimages is of concern in this thesis and since frequency domain methods are more robust thanspatial domain techniques all of the proposed watermarking algorithms are designed in thefrequency domain One of the four presented methods is based on wavelet transform In thisalgorithm a HWD based mask is designed to choose proper coefficients of the LL subband forembedding Human eye is less sensitive to modifications of 2D singularities and since Contourlettransform can extract 2D singularities better than wavelet hence the other proposed methods arebased on embedding in Contourlet coefficients To increase robustness two of the proposedschemes embed the watermark into singular values of Contourlet coefficients Since proper valueof strength factor has an important effect on fidelity and robustness of watermarked images in thisthesis a genetic algorithm is proposed to determine this strength parameter in the embedding phase The fitness function of genetic algorithm considers both fidelity and robustness of a watermarkedimage Three out of four proposed schemes are non blind methods and need the original image inthe extraction phase But one of the schemes is a blind algorithm and can extract the watermarkwithout having the original image Since sometimes the original image may not be available at theextraction phase blindness is a major advantage of this algorithm To increase robustness of theblind method embedding is done in DCT coefficients of Contourlet blocks Furthermore all theContourlet based methods benefit from multiple embedding of watermark that increases robustnessof proposed techniques The results of experiments show that proposed schemes have goodrobustness against usual image processing attacks while preserving fidelity of watermarked images Keywords Watermark watermarking robustness fidelity

شادرخ سماوي

محمدرضا احمدزاده، بهزاد نظري