Slides_Chapters_1_to_22PPT英文课件Slides_Chapter12

Chapter12Imagerestoration,PracticalImageandVideoProcessingUsingMATLAB,ByOgeMarquesCopyright2011byJohnWileyforD=(mn-1)/2:itisequivalenttothemedianfilter.Usedincaseswheretheimagehasbeencorruptedbymorethanonetypeofnoise,e.g.,salt-and-pepperandGaussian.,ByOgeMarquesCopyright2011byJohnWiley&Sons,Inc.Allrightsreserved.,NoisereductionRankfilters,Example12.5,ByOgeMarquesCopyright2011byJohnWiley&Sons,Inc.Allrightsreserved.,Noisereductionfrequencydomain,Mainapplication:reductionorremovalofperiodicnoise.Periodicnoiseatypeofnoisethatusuallyarisesasaresultofelectricalorelectromechanicalinterferenceduringtheimageacquisitionprocess.,ByOgeMarquesCopyright2011byJohnWiley&Sons,Inc.Allrightsreserved.,Noisereductionfrequencydomain,Bandrejectfilterattenuatesfrequencycomponentswithinacertainrange(thestopbandofthefilter)whileleavingallotherfrequencycomponentsuntouched(oramplifyingthembyacertaingain).Idealbandrejectfilter,ByOgeMarquesCopyright2011byJohnWiley&Sons,Inc.Allrightsreserved.,Noisereductionfrequencydomain,BandrejectfilterButterworthbandrejectfilterGaussianbandrejectfilter,ByOgeMarquesCopyright2011byJohnWiley&Sons,Inc.Allrightsreserved.,NoisereductionIdealbandrejectfilter,Example12.7,ByOgeMarquesCopyright2011byJohnWiley&Sons,Inc.Allrightsreserved.,Noisereductionfrequencydomain,BandpassfilterAllowscertainfrequencies(withinitspassband)tobepreservedwhileattenuatingallothers.Itis,ineffect,theoppositeofabandrejectfilter:,ByOgeMarquesCopyright2011byJohnWiley&Sons,Inc.Allrightsreserved.,Noisereductionfrequencydomain,Bandpassfilter(BPF)IdealButterworthGaussian,ByOgeMarquesCopyright2011byJohnWiley&Sons,Inc.Allrightsreserved.,Noisereductionfrequencydomain,NotchfilterSpecialkindoffrequencydomainfilterthatattenuates(orallows)frequencieswithinaneighborhoodaroundacenterfrequency.DuetothesymmetrypropertyoftheFouriertransform,thespectrumofnotchfiltersshowssymmetricpairsaroundtheorigin(exceptforanotchfilterlocatedattheorigin,ofcourse).,ByOgeMarquesCopyright2011byJohnWiley&Sons,Inc.Allrightsreserved.,Noisereductionfrequencydomain,Idealnotchfilter,ByOgeMarquesCopyright2011byJohnWiley&Sons,Inc.Allrightsreserved.,Noisereductionfrequencydomain,Butterworthnotchfilter,ByOgeMarquesCopyright2011byJohnWiley&Sons,Inc.Allrightsreserved.,Noisereductionfrequencydomain,Gaussiannotchfilter,ByOgeMarquesCopyright2011byJohnWiley&Sons,Inc.Allrightsreserved.,Noisereductionfrequencydomain,Toconvertanotchfilterthatrejectscertainfrequenciesintoonethatallowsthosesamefrequenciestopassonehastosimplycompute:whereHnp(u,v)isthetransferfunctionofthenotchpassfilterthatcorrespondstothenotchrejectfilterwhosetransferfunctionisHnr(u,v).,ByOgeMarquesCopyright2011byJohnWiley&Sons,Inc.Allrightsreserved.,Imagedeblurringtechniques,Goal:toprocessanimagethathasbeensubjecttoblurringcaused,e.g.,bycameramotionduringimagecaptureorpoorfocusingofthelenses.Simplesttechnique:inversefilteringwhere:1/H(u,v)istheFToftherestorationfilterProblems:Divisionbyzero0/0indeterminationIfthereisalsonoise,itwillheavilyinfluencethecalculations,ByOgeMarquesCopyright2011byJohnWiley&Sons,Inc.Allrightsreserved.,Imagedeblurringtechniques,InversefilteringDivisionbyzeroproblemhas2possiblesolutions:Applya(Butterworth)lowpassfilterwithtransferfunctionL(u,v)tothedivision,thuslimitingtherestorationtoarangeoffrequenciesbelowtherestorationcutofffrequency:Useconstraineddivision,whereathresholdvalueTischosensuchthat,if|H(u,v)|T,thedivisiondoesnottakeplaceandtheoriginalvalueiskeptuntouched,i.e.:,ByOgeMarquesCopyright2011byJohnWiley&Sons,Inc.Allrightsreserved.,Imagedeblurringtechniques,InversefilteringExample12.8,ByOgeMarquesCopyright2011byJohnWiley&Sons,Inc.Allrightsreserved.,Motiondeblurring,Motiondeblurringcanbeconsideredaspecialcaseofinversefiltering.ExampleofmotiondeblurringusinginversefilteringwithconstraineddivisionandthresholdT=0.05.Themotionblurredhasbeenremovedattheexpenseoftheappearanceofverticalartifacts.,ByOgeMarquesCopyright2011byJohnWiley&Sons,Inc.Allrightsreserved.,Imagedeblurringtechniques,Wienerfiltering(1942)Imagerestorationsolutionthatcanbeappliedtoimagesthathavebeensubjecttoadegradationfunctionandalsocontainnoise(worst-casescenario).Attempttomodeltheerrorintherestoredimagethroughstatisticalmethods,particularlytheminimummean-squareestimator:oncetheerrorismodeled,theaverageerrorismathematicallyminimized.ThetransferfunctionofaWienerfilterisgivenby:whereH(u,v)isthedegradationfunctionandKisaconstantusedtoapproximatetheamountofnoise.,ByOgeMarquesCopyright2011byJohnWiley&Sons,Inc.Allrightsreserved.,Imagedeblurringtechniques,Wienerfilterinthepresenceofblurandnoise(Example12.9),ByOgeMarquesCopyright2011byJohnWiley&Sons,Inc.Allrightsreserved.,Imagedeblurringtechniques,Wienerfilterinthepresenceofbluronly,ByOgeMarquesCopyright2011byJohnWiley&Sons,Inc.Allrightsreserved.,Imagedeblurringtechniques,ImagedeblurringinMATLAB:Wienerfilter:deconvwnrDeblurimageusingregularizedfilter:deconvregDeblurimageusingLucy-Richardsonmethod:dec