Visual Tracking

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1、ECE432-AdvancedComputerVisionNotesSeries7VisualTrackingYingWuElectrical&ComputerEngineeringNorthwesternUniversityEvanston,IL60208yingwu@ece.nwu.eduContents1GettingStart–BackgroundSubtraction22TemplateMatching32.1SSDandCross-Correlation...............

2、.............32.2Searchvs.Descent................................32.2.1Search...................................32.2.2TheDirectMethod............................43TwoPhilosophies53.1Bottom-upApproach...............................53.2Top-downApproach

3、...............................54AProbabilisticFramework64.1WhatisTracking?................................64.2FourElementsinTracking............................64.3AnexampleofObservationModel........................84.4TrackingasProbabilityPropagati

4、on......................85KalmanFiltering95.1KalmanFilteringforLinearDynamicSystems.................95.2Example:TrackingFeaturePoint........................106SequentialMonteCarlo126.1FactoredSampling................................126.2ImportanceSam

5、pling...............................1311GettingStart–BackgroundSubtractionInmanyvideosurveillanceapplications,camerasarefixedandweareinterestedintrackingthemotionoftheforeground,whichcouldbepeopleorcars.Obviously,framedifferenceonlygivesusaroughideaofw

6、hichregionsmaycontainmovingobjects,butsuchasimplemethodcanneithersperatetheforegroundfromthebackground,nortelluswhichimageregionsaremovingregions.Asaresult,doingsimpleframedifferencingwillnotoutputgoodtrackingresults.Backgroundsubtractionissuchatechni

7、quethattheforegroundregioncanbeseparatedfrombackgroundbymaintainingabackgroundmodel,andclassifyingeachpixelintoeitherforegroundandbackground.Theassumptionhereisthatthecameraismoreorlessfixedsuchthatwecanmaintainortrainabackgroundmodel.Generally,suchba

8、ckgroundmodelcanbepixel-wise,i.e.,eachpixelismodeledindependently.Foreachimagepixellocation,wecomparetheinputimagepixelanditsbackgroundmodelanddetermineitsclass.Asimpleapproachjustusesameanimageasthebackground,thosepixelswhichdeviatefromthecorrespond