外文文献资料(Canny算子)

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1、苏州大学本科生毕业设计（论文）附件：外文文献资料与中文翻译稿外文文献资料Cannyedgedetector1.CannyedgedetectorIntroductionTheCannyedgedetectionoperatorwasdevelopedbyJohnF.Cannyin1986andusesamulti-stagealgorithmtodetectawiderangeofedgesinimages.Mostimportantly,Cannyalsoproducedacomputationaltheoryofedgedetectionexplainingwhythetechniq

2、ueworks.2.DevelopmentoftheCannyalgorithmCanny'saimwastodiscovertheoptimaledgedetectionalgorithm.Inthissituation,an"optimal"edgedetectormeans:lgooddetection–thealgorithmshouldmarkasmanyrealedgesintheimageaspossible.lgoodlocalization–edgesmarkedshouldbeascloseaspossibletotheedgeintherealimage.lmini

3、malresponse–agivenedgeintheimageshouldonlybemarkedonce,andwherepossible,imagenoiseshouldnotcreatefalseedges.TosatisfytheserequirementsCannyusedthecalculusofvariations–atechniquewhichfindsthefunctionwhichoptimizesagivenfunctional.The8苏州大学本科生毕业设计（论文）附件：外文文献资料与中文翻译稿optimalfunctioninCanny'sdetectoris

4、describedbythesumoffourexponentialterms,butcanbeapproximatedbythefirstderivativeofaGaussian.3.StagesoftheCannyalgorithm3.1NoisereductionTheCannyedgedetectorusesafilterbasedonthefirstderivativeofaGaussian,becauseitissusceptibletonoisepresentonrawunprocessedimagedata,sotobeginwith,therawimageisconv

5、olvedwithaGaussianfilter.Theresultisaslightlyblurredversionoftheoriginalwhichisnotaffectedbyasinglenoisypixeltoanysignificantdegree.3.2FindingtheintensitygradientoftheimageAnedgeinanimagemaypointinavarietyofdirections,sotheCannyalgorithmusesfourfilterstodetecthorizontal,verticalanddiagonaledgesin

6、theblurredimage.Theedgedetectionoperator(Roberts,Prewitt,Sobelforexample)returnsavalueforthefirstderivativeinthehorizontaldirection(Gy)andtheverticaldirection(Gx).Fromthistheedgegradientanddirectioncanbedetermined.3.3TracingedgesthroughtheimageandhysteresisthresholdingIntensitygradientswhicharela

7、rgearemorelikelytocorrespondtoedgesthaniftheyaresmall.Itisinmostcasesimpossibletospecifyathresholdatwhicha8苏州大学本科生毕业设计（论文）附件：外文文献资料与中文翻译稿givenintensitygradientswitchesfromcorrespondingtoanedgeintonotdoingso.ThereforeCa