数字图像处理-冈萨雷斯-课件(英文)Chapter02Eng 数字图像基础

DigitalImageProcessingChapter2:DigitalImageFundamental6June2007WhatisDigitalImageProcessing?ProcessingofamultidimensionalpicturesbyadigitalcomputerWhyweneedDigitalImageProcessing?1.Torecordandstoreimages2.Toenhanceimagesusingmathematics3.Toanalysisimages4.Tosynthesizeimages5.TocreatecomputervisionsystemsDigitalImageDigitalimage=amultidimensionalarrayofnumbers(suchasintensityimage)orvectors(suchascolorimage)Eachcomponentintheimagecalledpixelassociateswiththepixelvalue(asinglenumberinthecaseofintensityimagesoravectorinthecaseofcolorimages).3987153222132515372669281610103965655442475421679654324356706599876532924385856796906078567099VisualPerception:HumanEye(PicturefromMicrosoftEncarta2000)CrossSectionoftheHumanEye(ImagesfromRafaelC.GonzalezandRichardE.Wood,DigitalImageProcessing,2ndEdition.1.Thelenscontains60-70%water,6%offat.2.Theirisdiaphragmcontrolsamountoflightthatenterstheeye.3.Lightreceptorsintheretina-About6-7millionsconesforbrightlightvisioncalledphotopic-Densityofconesisabout150,000elements/mm2.-Conesinvolveincolorvision.-Conesareconcentratedinfoveaabout1.5x1.5mm2.-About75-150millionsrodsfordimlightvisioncalledscotopic-Rodsaresensitivetolowleveloflightandarenotinvolvedcolorvision.4.Blindspotistheregionofemergenceoftheopticnervefromtheeye.VisualPerception:HumanEye(cont.)RangeofRelativeBrightnessSensationSimutaneousrangeissmallerthanTotaladaptationrange(ImagesfromRafaelC.GonzalezandRichardE.Wood,DigitalImageProcessing,2ndEdition.DistributionofRodsandConesintheRetina(ImagesfromRafaelC.GonzalezandRichardE.Wood,DigitalImageProcessing,2ndEdition.ImageFormationintheHumanEye(PicturefromMicrosoftEncarta2000)(ImagesfromRafaelC.GonzalezandRichardE.Wood,DigitalImageProcessing,2ndEdition.PositionIntensityBrightnessAdaptationofHumanEye:MachBandEffectMachBandEffectIntensitiesofsurroundingpointseffectperceivedbrightnessateachpoint.Inthisimage,edgesbetweenbarsappearbrighterontherightsideanddarkerontheleftside.(ImagesfromRafaelC.GonzalezandRichardE.Wood,DigitalImageProcessing,2ndEdition.InareaA,brightnessperceivedisdarkerwhileinareaBisbrighter.ThisphenomenoniscalledMachBandEffect.PositionIntensityABMachBandEffect(Cont)Simultaneouscontrast.Allsmallsquareshaveexactlythesameintensitybuttheyappearprogressivelydarkerasbackgroundbecomeslighter.BrightnessAdaptationofHumanEye:SimultaneousContrastSimultaneousContrast(ImagesfromRafaelC.GonzalezandRichardE.Wood,DigitalImageProcessing,2ndEdition.Opticalillusion(ImagesfromRafaelC.GonzalezandRichardE.Wood,DigitalImageProcessing,2ndEdition.VisibleSpectrum(ImagesfromRafaelC.GonzalezandRichardE.Wood,DigitalImageProcessing,2ndEdition.ImageSensorsSinglesensorLinesensorArraysensor(ImagesfromRafaelC.GonzalezandRichardE.Wood,DigitalImageProcessing,2ndEdition.ImageSensors:SingleSensor(ImagesfromRafaelC.GonzalezandRichardE.Wood,DigitalImageProcessing,2ndEdition.ImageSensors:LineSensorFingerprintsweepsensorComputerizedAxialTomography(ImagesfromRafaelC.GonzalezandRichardE.Wood,DigitalImageProcessing,2ndEdition.CCDKAF-3200EfromKodak.(2184x1472pixels,Pixelsize6.8microns2)Charge-CoupledDevice(CCD)wUsedforconvertacontinuousimageintoadigitalimagewContainsanarrayoflightsensorswConvertsphotonintoelectricchargesaccumulatedineachsensorunitImageSensors:ArraySensorHorizontalTransportationRegisterOutputGateAmplifierVerticalTransportRegisterGateVerticalTransportRegisterGateVerticalTransportRegisterGatePhotositesOutputImageSensor:InsideCharge-CoupledDeviceImageSensor:HowCCDworksabcghidefabcghidefabcghidefVerticalshiftHorizontalshiftImagepixelHorizontaltransportregisterOutputImage“Aftersnowstorm”FundamentalsofDigitalImagesf(x,y)xywAnimage:amultidimensionalfunctionofspatialcoordinates.wSpatialcoordinate:(x,y)for2Dcasesuchasphotograph,(x,y,z)for3DcasesuchasCTscanimages(x,y,t)formovieswThefunctionfmayrepresentintensity(formonochromeimages)orcolor(forcolorimages)orotherassociatedvalues.OriginDigitalImagesDigitalimage:animagethathasbeendiscretizedbothinSpatialcoordinatesandassociatedvalue.wConsistof2sets:(1)apointsetand(2)avaluesetwCanberepresentedintheformI={(x,a(x)):xX,a(x)F}whereXandFareapointsetandvalueset,respectively.wAnelementoftheimage,(x,a(x))iscalledapixelwhere-xiscalledthepixellocationand-a(x)isthepixelvalueatthelocationxConventionalCoordinateforImageRepresentation(ImagesfromRafaelC.GonzalezandRichardE.Wood,DigitalImageProcessing,2ndEdition.DigitalImageTypes:IntensityImageIntensityimageormonochromeimageeachpixelcorrespondstolightintensitynormallyrepresentedingrayscale(graylevel).398715322213251537266928161010Grayscalevalues3987153222132515372669281610103965655442475421679654324356706599876532924385856796906078567099DigitalImageTypes:RGBImageColorimageorRGBimage:eachpixelcontainsavectorrepresentingred,greenandbluecomponents.RGBcomponentsImageTypes:BinaryImageBinaryimageorblackandwhiteimageEachpixelcontainsonebit:1representwhite0representsblack1111111100000000BinarydataImageTypes:IndexImageIndeximageEachpixe