数字图像处理-冈萨雷斯-课件 英文 Chapter11 表 示与 描述.ppt

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1、DigitalImageProcessingChapter11:ImageDescriptionandRepresentation12September2007ImageRepresentationandDescription?Objective:Torepresentanddescribeinformationembeddedinanimageinotherformsthataremoresuitablethantheimageitself.Benefits:-Easiertounderstand-Requirefewermemory

2、,fastertobeprocessed-More“readytobeused”Whatkindofinformationwecanuse?-Boundary,shape-Region-Texture-RelationbetweenregionsShapeRepresentationbyUsingChainCodesChaincodes:representanobjectboundarybyaconnectedsequenceofstraightlinesegmentsofspecifiedlengthanddirection.4-di

3、rectionalchaincode8-directionalchaincodeWhywefocusonaboundary?Theboundaryisagoodrepresentationofanobjectshapeandalsorequiresafewmemory.(ImagesfromRafaelC.GonzalezandRichardE.Wood,DigitalImageProcessing,2ndEdition.ExamplesofChainCodesObjectboundary(resampling)Boundaryvert

4、ices4-directionalchaincode8-directionalchaincode(ImagesfromRafaelC.GonzalezandRichardE.Wood,DigitalImageProcessing,2ndEdition.TheFirstDifferenceofaChainCodesProblemofachaincode:achaincodesequencedependsonastartingpoint.Solution:treatachaincodeasacircularsequenceandredefi

5、nethestartingpointsothattheresultingsequenceofnumbersformsanintegerofminimummagnitude.Thefirstdifferenceofachaincode:countingthenumberofdirectionchange(incounterclockwise)between2adjacentelementsofthecode.Example:1230Example:-achaincode:10103322-Thefirstdifference=313303

6、0-Treatingachaincodeasacircularsequence,wegetthefirstdifference=33133030Chaincode:Thefirstdifference011022033231202213Thefirstdifferenceisrotationalinvariant.PolygonApproximationObjectboundaryMinimumperimeterpolygonRepresentanobjectboundarybyapolygonMinimumperimete

7、rpolygonconsistsoflinesegmentsthatminimizedistancesbetweenboundarypixels.(ImagesfromRafaelC.GonzalezandRichardE.Wood,DigitalImageProcessing,2ndEdition.PolygonApproximation:SplittingTechniques1.Findthelinejoiningtwoextremepoints0.Objectboundary2.Findthefarthestpointsfromt

8、heline3.Drawapolygon(ImagesfromRafaelC.GonzalezandRichardE.Wood,DigitalImageProcessing,2ndEdition.Dista