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页数:6页
时间:2019-05-27
《Symmetry and asymmetry from local phase》由会员上传分享,免费在线阅读,更多相关内容在行业资料-天天文库。
1、SymmetryandAsymmetryfromLocalPhasePeterKovesiDepartmentofComputerScienceTheUniversityofWesternAustraliaNedlandsW.A.6907pk@cs.uwa.edu.auAbstract.Symmetryisanimportantmechanismbywhichweidentifythestructureofobjects.Man-madeobjects,plantsandanimalsareusuallyhighlyrecognizablefromthesymme
2、try,orpartialsymmetriesthattheyoftenexhibit.Twodi±cultiesfoundinmostsymmetrydetectionalgorithmsare¯rstly,thattheyusuallyrequireobjectstobesegmentedpriortoanysymmetryanalysis,andsecondly,thattheydonotprovideanyabsolutemeasureofthedegreeofsymmetryatanypointinanimage.Thispaperpresentsane
3、wmeasureofsymmetrythatisbasedontheanalysisoflocalfrequencyinformation.Itisshownthatpointsofsymmetryandasymmetrygiverisetoeasilyrecognizedpatternsoflocalphase.Thisphaseinformationcanbeusedtoconstructacontrastinvariantmeasureofsymmetrythatdoesnotrequireanypriorrecognitionorsegmentationo
4、fobjects.Keywords:ComputerVision,Symmetry,Asymmetry,LocalPhase,QuadratureFilters1IntroductionUnderthemostgeneralde¯nitionofsymmetryanobjectisconsideredsymmetricifitremainsinvariantundersometransformation.Twoformsofsymmetrythatwecanreadilyidentifyinimagesarebilateralsymmetryandrotation
5、alsymmetry.Anobjectexhibitsbilateralsymmetryifitremainsinvariantwithrespecttore°ectionaboutsomeaxis.Anobjecthasrotationalsymmetryifitremainsinvariantwithrespecttorotationsaboutsomeaxis.Thispaperwillmainlyconsiderbilateralsymmetryandinthefollowingdiscussionwherethewordsymmetryisusedits
6、houldbetakentomeanbilateralsymmetry.Symmetryisanimportantmechanismbywhichweidentifythestructureofobjects.Man-madeobjects,plantsandanimalsareusuallyhighlyrecognizablefromthesymmetry,orpartialsymmetriesthattheyoftenexhibit.Alimitednumberofapproacheshavebeentriedinthedetectionofsymmetryi
7、nimages.Afundamentalweaknessfoundinmostisthattheyrequireobjectstobesegmentedpriortoanysymmetryanalysis.ForexampleAtallah[1]describesanalgorithmthatrequiresobjectstoberepresentedintermsofpoints,linesegmentsandcircles.Morphologicaltechniquessuchasmedialaxistransforms,thinning,and`grass¯
8、re'al
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