数字图像处理-冈萨雷斯-课件(英文)Chapter02Eng 数字图像基础

DigitalImageProcessingChapter2:DigitalImageFundamental6June2007,WhatisDigitalImageProcessing?,Processingofamultidimensionalpicturesbyadigitalcomputer,WhyweneedDigitalImageProcessing?,TorecordandstoreimagesToenhanceimagesusingmathematicsToanalysisimagesTosynthesizeimagesTocreatecomputervisionsystems,DigitalImage,Digitalimage=amultidimensionalarrayofnumbers(suchasintensityimage)orvectors(suchascolorimage),Eachcomponentintheimagecalledpixelassociateswiththepixelvalue(asinglenumberinthecaseofintensityimagesoravectorinthecaseofcolorimages).,VisualPerception:HumanEye,(PicturefromMicrosoftEncarta2000),CrossSectionoftheHumanEye,(ImagesfromRafaelC.GonzalezandRichardE.Wood,DigitalImageProcessing,2ndEdition.,Thelenscontains60-70%water,6%offat.Theirisdiaphragmcontrolsamountoflightthatenterstheeye.Lightreceptorsintheretina-About6-7millionsconesforbrightlightvisioncalledphotopic-Densityofconesisabout150,000elements/mm2.-Conesinvolveincolorvision.-Conesareconcentratedinfoveaabout1.5x1.5mm2.-About75-150millionsrodsfordimlightvisioncalledscotopic-Rodsaresensitivetolowleveloflightandarenotinvolvedcolorvision.4.Blindspotistheregionofemergenceoftheopticnervefromtheeye.,VisualPerception:HumanEye(cont.),RangeofRelativeBrightnessSensation,SimutaneousrangeissmallerthanTotaladaptationrange,(ImagesfromRafaelC.GonzalezandRichardE.Wood,DigitalImageProcessing,2ndEdition.,DistributionofRodsandConesintheRetina,(ImagesfromRafaelC.GonzalezandRichardE.Wood,DigitalImageProcessing,2ndEdition.,ImageFormationintheHumanEye,(PicturefromMicrosoftEncarta2000),(ImagesfromRafaelC.GonzalezandRichardE.Wood,DigitalImageProcessing,2ndEdition.,BrightnessAdaptationofHumanEye:MachBandEffect,MachBandEffect,Intensitiesofsurroundingpointseffectperceivedbrightnessateachpoint.Inthisimage,edgesbetweenbarsappearbrighterontherightsideanddarkerontheleftside.,(ImagesfromRafaelC.GonzalezandRichardE.Wood,DigitalImageProcessing,2ndEdition.,InareaA,brightnessperceivedisdarkerwhileinareaBisbrighter.ThisphenomenoniscalledMachBandEffect.,Position,Intensity,A,B,MachBandEffect(Cont),Simultaneouscontrast.Allsmallsquareshaveexactlythesameintensitybuttheyappearprogressivelydarkerasbackgroundbecomeslighter.,BrightnessAdaptationofHumanEye:SimultaneousContrast,SimultaneousContrast,(ImagesfromRafaelC.GonzalezandRichardE.Wood,DigitalImageProcessing,2ndEdition.,Opticalillusion,(ImagesfromRafaelC.GonzalezandRichardE.Wood,DigitalImageProcessing,2ndEdition.,VisibleSpectrum,(ImagesfromRafaelC.GonzalezandRichardE.Wood,DigitalImageProcessing,2ndEdition.,ImageSensors,Singlesensor,Linesensor,Arraysensor,(ImagesfromRafaelC.GonzalezandRichardE.Wood,DigitalImageProcessing,2ndEdition.,ImageSensors:SingleSensor,(ImagesfromRafaelC.GonzalezandRichardE.Wood,DigitalImageProcessing,2ndEdition.,ImageSensors:LineSensor,Fingerprintsweepsensor,ComputerizedAxialTomography,(ImagesfromRafaelC.GonzalezandRichardE.Wood,DigitalImageProcessing,2ndEdition.,CCDKAF-3200EfromKodak.(2184x1472pixels,Pixelsize6.8microns2),Charge-CoupledDevice(CCD),wUsedforconvertacontinuousimageintoadigitalimagewContainsanarrayoflightsensorswConvertsphotonintoelectricchargesaccumulatedineachsensorunit,ImageSensors:ArraySensor,HorizontalTransportationRegister,OutputGate,Amplifier,Photosites,Output,ImageSensor:InsideCharge-CoupledDevice,ImageSensor:HowCCDworks,Verticalshift,Horizontalshift,Imagepixel,Horizontaltransportregister,Output,Image“Aftersnowstorm”,FundamentalsofDigitalImages,wAnimage:amultidimensionalfunctionofspatialcoordinates.wSpatialcoordinate:(x,y)for2Dcasesuchasphotograph,(x,y,z)for3DcasesuchasCTscanimages(x,y,t)formovieswThefunctionfmayrepresentintensity(formonochromeimages)orcolor(forcolorimages)orotherassociatedvalues.,DigitalImages,Digitalimage:animagethathasbeendiscretizedbothinSpatialcoordinatesandassociatedvalue.wConsistof2sets:(1)apointsetand(2)avaluesetwCanberepresentedintheformI=(x,a(x):xX,a(x)FwhereXandFareapointsetandvalueset,respectively.wAnelementoftheimage,(x,a(x)iscalledapixelwhere-xiscalledthepixellocationand-a(x)isthepixelvalueatthelocationx,ConventionalCoordinateforImageRepresentation,(ImagesfromRafaelC.GonzalezandRichardE.Wood,DigitalImageProcessing,2ndEdition.,DigitalImageTypes:IntensityImage,Intensityimageormonochromeimageeachpixelcorrespondstolightintensitynormallyrepresentedingrayscale(graylevel).,Grayscalevalues,DigitalImageTypes:RGBImage,ColorimageorRGBimage:eachpixelcontainsavectorrepresentingred,greenandbluecomponents.,RGBcomponents,ImageTypes:BinaryImage,BinaryimageorblackandwhiteimageEachpixelcontainsonebit:1representwhite0representsblack,Binarydata,ImageTypes:IndexImage,IndeximageEachpixelcontainsindexnumberpointingtoacolorinacolortable,Indexvalue,ColorTable,DigitalImageAcquisitionProcess,(ImagesfromRafaelC.GonzalezandRichardE.Wood,DigitalImageProcessing,2ndEdition.,GeneratingaDigitalImage,(ImagesfromRafaelC.GonzalezandRichardE.Wood,DigitalImageProcessing,2ndEdition.,ImageSamplingandQuantization,Imagesampling:discretizeanimageinthespatialdomainSpatialresolution/imageresolution:pixelsizeornumberofpixels,(ImagesfromRafaelC.GonzalezandRichardE.Wood,DigitalImageProcessing,2ndEdition.,Howtochoosethespatialresolution,Originalimage,Sampledimage,Undersampling,welostsomeimagedetails!,Spatialresolution,Howtochoosethespatialresolution:NyquistRate,Originalimage,Nodetailislost!,NyquistRate:SpatialresolutionmustbelessorequalhalfoftheminimumperiodoftheimageorsamplingfrequencymustbegreaterorEqualtwiceofthemaximumfrequency.,2mm,1mm,Samplingrate:5samples/sec,AliasedFrequency,Twodifferentfrequenciesbutthesameresults!,EffectofSpatialResolution,EffectofSpatialResolution,(ImagesfromRafaelC.GonzalezandRichardE.Wood,DigitalImageProcessing,2ndEdition.,MoirePatternEffect:SpecialCaseofSampling,Moirepatternsoccurwhenfrequenciesoftwosuperimposedperiodicpatternsareclosetoeachother.,(ImagesfromRafaelC.GonzalezandRichardE.Wood,DigitalImageProcessing,2ndEdition.,EffectofSpatialResolution,(ImagesfromRafaelC.GonzalezandRichardE.Wood,DigitalImageProcessing,2ndEdition.,Canweincreasespatialresolutionbyinterpolation?,Downsamplingisanirreversibleprocess.,(ImagesfromRafaelC.GonzalezandRichardE.Wood,DigitalImageProcessing,2ndEdition.,ImageQuantization,Imagequantization:discretizecontinuouspixelvaluesintodiscretenumbersColorresolution/colordepth/levels:-No.ofcolorsorgraylevelsor-No.ofbitsrepresentingeachpixelvalue-No.ofcolorsorgraylevelsNcisgivenby,whereb=no.ofbits,Quantizationfunction,Lightintensity,Quantizationlevel,0,1,2,Nc-1,Nc-2,Darkest,Brightest,EffectofQuantizationLevels,256levels,128levels,32levels,64levels,EffectofQuantizationLevels(cont.),16levels,8levels,2levels,4levels,Howtoselectthesuitablesizeandpixeldepthofimages,Lowdetailimage,Mediumdetailimage,Highdetailimage,Lenaimage,Cameramanimage,Tosatisfyhumanmind1.Forimagesofthesamesize,thelowdetailimagemayneedmorepixeldepth.2.Asanimagesizeincrease,fewergraylevelsmaybeneeded.,Theword“suitable”issubjective:dependingon“subject”.,(ImagesfromRafaelC.GonzalezandRichardE.Wood,DigitalImageProcessing,2ndEdition.,BasicRelationshipofPixels,x,y,(0,0),Conventionalindexingmethod,NeighborsofaPixel,p,4-neighborsofp:,(x-1,y)(x+1,y)(x,y-1)(x,y+1),Neighborhoodrelationisusedtotelladjacentpixels.Itisusefulforanalyzingregions.,Note:qN4(p)impliespN4(q),4-neighborhoodrelationconsidersonlyverticalandhorizontalneighbors.,p,(x+1,y),(x-1,y),(x,y-1),(x,y+1),(x+1,y-1),(x-1,y-1),(x-1,y+1),(x+1,y+1),NeighborsofaPixel(cont.),8-neighborsofp:,(x-1,y-1)(x,y-1)(x+1,y-1)(x-1,y)(x+1,y)(x-1,y+1)(x,y+1)(x+1,y+1),N8(p)=,8-neighborhoodrelationconsidersallneighborpixels.,p,(x+1,y-1),(x-1,y-1),(x-1,y+1),(x+1,y+1),Diagonalneighborsofp:,ND(p)=,(x-1,y-1)(x+1,y-1)(x-1,y+1)(x+1,y+1),NeighborsofaPixel(cont.),Diagonal-neighborhoodrelationconsidersonlydiagonalneighborpixels.,Connectivity,Connectivityisadaptedfromneighborhoodrelation.Twopixelsareconnectediftheyareinthesameclass(i.e.thesamecolororthesamerangeofintensity)andtheyareneighborsofoneanother.Forpandqfromthesameclassw4-connectivity:pandqare4-connectedifqN4(p)w8-connectivity:pandqare8-connectedifqN8(p)wmixed-connectivity(m-connectivity):pandqarem-connectedifqN4(p)orqND(p)andN4(p)N4(q)=,Adjacency,Apixelpisadjacenttopixelqistheyareconnected.TwoimagesubsetsS1andS2areadjacent