SURF：Speed Up Robust Feature.ppt

1 SURF SpeededUpRobustFeatures ECCV2006 HerbertBay TinneTuytelaars andLucVanGool GroupMeetingPresentedbyWyman10 14 2006 2 Background LocalinvariantInterestpointdetector descriptorForfindingcorrespondencesbetweentwoimagesofthesamesceneorobjectManyapplications including3Dreconstruction imageretrievalandobjectrecognitionSIFTisoneofthebestbutslowImageofsize1000 x700describedinaround6seconds actualcostdependsonthe featuresgenerated 4000inthiscase 128 Dfeaturevectors 3 Motivation FastinterestpointdetectionDistinctiveinterestpointdescriptionSpeeded updescriptormatchingInvarianttocommonimagetransformations ImagerotationScalechangesIlluminationchangeSmallchangeinViewpoint 4 Methodology UsingintegralimagesformajorspeedupIntegralImage summedareatables isanintermediaterepresentationfortheimageandcontainsthesumofgrayscalepixelvaluesofimageSecondorderderivativeandHaar waveletresponse Costfouradditionsoperationonly 5 Detection Hessian basedinterestpointlocalizationLxx x y istheLaplacianofGaussianoftheimageItistheconvolutionoftheGaussiansecondorderderivativewiththeimageLindebergshowedGaussianfunctionisoptimalforscale spaceanalysisThispaperarguesthatGaussianisoverratedsincethepropertythatnonewstructurescanappearwhilegoingtolowerresolutionisnotprovenin2Dcase 6 Detection Approximatedsecondorderderivativeswithboxfilters mean averagefilter 7 Detection Scaleanalysiswithconstantimagesize 9x9 15x15 21x21 27x27 39x39 51x51 1stoctave2ndoctave 8 Detection Non maximumsuppressionandinterpolationBlob likefeaturedetector 9 Description OrientationAssignment Circularneighborhoodofradius6saroundtheinterestpoint s thescaleatwhichthepointwasdetected Sidelength 4sCost6operationtocomputetheresponse xresponseyresponse 10 Description DominantorientationTheHaarwaveletresponsesarerepresentedasvectorsSumallresponseswithinaslidingorientationwindowcoveringanangleof60degreeThetwosummedresponseyieldanewvectorThelongestvectoristhedominantorientationSecondlongestis ignored 11 Description Splittheinterestregionupinto4x4squaresub regionswith5x5regularlyspacedsamplepointsinsideCalculateHaarwaveletresponsedxanddyWeighttheresponsewithaGaussiankernelcenteredattheinterestpointSumtheresponseovereachsub regionfordxanddyseparately featurevectoroflength32Inordertobringininformationaboutthepolarityoftheintensitychanges extractthesumofabsolutevalueoftheresponses featurevectoroflength64Normalizethevectorintounitlength 12 Description 13 Description SURF 128Thesumofdxand dx arecomputedseparatelyfordy0Similarlyforthesumofdyand dy Thisdoublesthelengthofafeaturevector 14 Matching FastindexingthroughthesignoftheLaplacianfortheunderlyinginterestpointThesignoftraceoftheHessianmatrixTrace Lxx LyyEither0or1 Hardthresholding mayhaveboundaryeffect Inthematchingstage comparefeaturesiftheyhavethesametypeofcontrast sign 15 ExperimentalResults 16 ExperimentalResults Viewpointchangeof30degrees 17 ExperimentalResults 18 ExperimentalResults 1 Wall2 Boat3 Bikes4 Trees 19 Analysis IhavecarriedoutabenchmarkonSURFandSIFTusingtheVisualGeometryGroupDatasetSURF Fast Hessiandetector SURFdescriptorSIFT DOGdetector SIFTdescriptor 20 Analysis 21 Analysis SURFisgoodathandlingseriousblurringhandlingimagerotationSURFispoorathandlingviewpointchangehandlingilluminationchangeSURFisalwaysbettertha