中值滤波器脉冲噪声毕业论文中英文资料外文翻译文献Word格式.docx
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中值滤波器脉冲噪声毕业论文中英文资料外文翻译文献Word格式.docx
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Abstract-Aninproved2-Dmedianfilteremployingmultishellconcepttosuppressimpulsenoise,ispresented.Theperformanceofproposedfilterisevaluatedoverimage‘LENA’,TheimpulsivenoiseisaddedusingMATLAButility.Themodifiedstrategyreducesthemnuberofreplacementandresultsinbetterperformanceandsimplehardwarerealizationthatissuitableforon-lineimplementation.
Indexterms-MedianFilter,Multi-shellMedianFilter,ImpulseNoise
I.INTRODUCTION
InTVandotherimagingsystems,impulsenoiseisacommonimpairment.ThestandardT.V.Broadcastsignalisoftencontaminatedwithimpulsivenoisearisingfromvarioussourcessuchashouseholdelectricalapplianceandatmosphericdisturbances.Broadbandingofthesignalfurtherincreasesthelevelofimpulsivenoise.Variousfiltersareproposedtosuppresssuchimpairments[1].Themedianfilter(MF)[1-2]iswidelyusedforimpulsenoisesuppressionandthemultishellmedianfilter(MMF)[3]introducestheconceptofmissinglinerecovery.Althoughthesefiltershavesatisfactoryperformance,MMFfailstofiltertwoimpulsenoisesinthesameprossingwindow.Moveover,thesefilterstendtoblurtheimagesduetotoomanyreplacements.C.J.Juanproposedamodifiedmultishellmedianfilter(MMMF)[4],whichremovesmostoftheshortcomingsassociatedwiththeMFandtheMMF.However,itisobservedthatundercertaincondions,tobediscussedinthefollowsections,MMMFfailstoperformthedesiredfilteringoperation.Moreover,thenumberofcalculations/replacementsinvovedonthebasisofMIN/MAXconditionsisstilltoolargeandmakesthefilterdifficulttorealize,particulariyforrealtimeapplications.
Inthispaper,thethresholdstrtegyofMMMFismodifiedsothat:
(a)effectivenoisefilteringoperationsareperformedunderallconditions,and
(b)numberofcalculations/replacementsisreducedandsimplified.
Thisresultsinasimplehardwarerealizationofthefilter.
II.PROPOSEDMODIFICATION
Considera3x3-processingwindow,withP5asthecentralpixel,asshowninFigure1.
P1
P2
P3
P4
P5
P6
P7
P8
P9
Fig.1.A3x3processingwindow
TheoutputofMMMFasproposedin[4]is
Output(X,Y)=Max(P2,P8)ifP5﹥Max[S]
P5ifMin[s]﹤Max[S]
Min(P2,P8)ifP5﹤Max[S]
(1)
WhereSisthesetofsamplessurroundingcentralpixelsexcept(P4.P6)i.e.
S={P1,P2,P3,P7,P8,P9}
(2)
TheprincipleinvovedinthereplacementstrategyofEquation
(1)isthatifP5iscorruptedbynoise,itisbettertoreplaceitsgraylevelbyP2orP8thanbyusingMin[S]orMax[S].also,duetomissinglineserror,sinceP4andP6maybelost,theyarenotconsideredinEquation
(2).
ThelimitationofEquation
(1)isthatwhenMin[S]orMax[S]arealsocorruptedbyimpulsenoise,i.e.eitherMin[S]orMax[S]isequaltoP5,Equation
(1)failstoperformthedesiredfilteringoperation.ToovercomethislimitationfollowingmodificationsinthereplacementstrategyofEquation
(1),areproposed.
Output(X,Y)=Max(P2,P8)ifP5≥Max[S]
P5ifMin[s]<P5<Max[S]
Min(P2,P8)ifP5≤Max[S](3)
Ithasbeenobservedthatmorethan70-80%pointsinanimage,thegrayleveldiatancesofP5from(P2orP8)andfromMax[S]arebelow16.ThisisshowninFig.2fortheimage‘LENA’.Thisfactisusedtofurtherreduceunnessaryreplacements,therebyreducingthebluringoftheimages.ThustakingintoconsidertionofFigure(3)canbefurthermodifiedas
Output(X,Y)=Max(P2,P8)ifP5-Max[S]≥16
Max(P2,P8)ifMin[s]-P5≥16
P5otherwise(4)
Equation4indicatesthatreplacingactiontakesplaceonlywhenthedistancebetweenP5andMin[S]orMax[S]isnosmallerthan16.Thisstrtegythusavoidsthenecessaryreplacementsandreducesblurringoftheimages.Moreover,itcanbeimplementedusingsimplecomparatorsandsubtractors.
Grayleveldistances
Fig.2.Grayleveldistancesbetweencentralpointanditsneighboringpointsfortheimage‘LENNA’
Ⅲ.RESULTS
Figure3showstheoriginalimage‘LENNA’andFigure4showsthesameimagewhencorruptedwithimpulsenoise.ResultsofmedianfilterandtheproposedfilteraregiveninFigures5and6,respectively.ComparingFigures5and6,itisobservedthattheresultoftheproposedfilterismuchbetterthanthoseobtainedusingthemedianfilter.Aithough,themedianfilterremovetheimpulsivemoiseeffectively,however,theimagegetsblurred.Theproposedfilterremovestheimpulsivenoiseandalsopreservesthedetailsoftheimage.
Amultishellfilteremployingthemodifiedreplacementstrategyispresentdeinthispaper.Themodifiedfiltereffectivelysuppressestheinpulsemoise.Itusesthresholdconditionsthatrequirefewercomparisonsandreplacementsandisfasterascomparedtotheothermultishellmedianfilters.moreover,itcanberealizedusingsimplecomparators
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