[日语学习]Digital Image Processing of charpter.ppt

6ColorImageProcessing XuCunlu 许存禄 clxu InstituteofCircuitandSystemNovember 2006 Itisonlyafteryearsofpreparationthattheyoungartistshouldtouchcolor notcoloruseddescriptively thatis butasameansofpersonalexpression HenriMatisse Preview Twoprincipalfactorsmotivatecolorimageprocessingresearch 1 ColorisapowerfuldescriptorSimplifiesobjectidentificationSimplifiesextractionfromascene 2 Humanscandiscernthousandsofcolorshadesandintensity morethan7milliondifferentcolors comparedtoaboutonlytwodozenshadesofgrayBeimportanttomanualimageanalysis TwocategoriesofCIP Full colorprocessingTheimagesinquestiontypicallyareacquiredwithafull colorsensor suchascolorTVcamera colorscanner Developingstep Publishing Visualization InternetPseudo colorprocessingAssigningacolortoaparticularmonochromeintensityorrangeofintensitiesMostdigitalcolorimageprocessing Outline 6 1ColorFundamentals6 2ColorModels6 3Pseudo colorImageProcessing6 4BasicsofFull ColorImageProcessing 6 1ColorFundamentals Theprocessfollowedbythehumanbraininperceivingandinterpretingcolorisaphysiopsychologicalphenomenonthatisnotyetfullyunderstood Physicalnatureofcolorcanbeexpressedonaformalbasissupportedbyexperimentalandtheoreticalresults ColorSpectrum In1666 Newtondiscoveredthatlightconsistsofacontinuousspectrumofcolors Violet Blue Green Yellow Orange andRedBlendssmoothlyintothenext VisualSpectrum Thecolorsperceivedinanobjectaredeterminedbythenatureofthelightreflectedfromtheobject White reflectslightthatisbalancedinallvisiblewavelengthsSomeshadesofcolor reflectalimitedrangeofthevisiblespectrum Characterizationoflight CharacterizationoflightiscentraltothescienceofcolorAchromaticOnlyattributeisintensity oramount WhatviewersseeonablackandwhiteTVset GraylevelChromaticlightApproximately400to700nm ChromaticLight ThreebasicquantitiesRadiance Thetotalamountofenergythatflowsfromthelightsource MeasureunitWatts W LuminanceAmeasureoftheamountofenergyanobserverperceives Measureunitlumens lm BrightnessSubjectivedescriptorImpossibletomeasureactually ColorVision Conesarethesensorsintheeyeresponsibleforcolorvision 6to7millionconescanbedividedintothreeprincipalsensingcategories Approximately65 red33 green2 blue blueconesarethemostsensitive Illustration PrimaryColors CIEStandardsetBlue 435 8nmGreen 546 1nmRed 700nmNosinglecolormaybecalledred greenorblue Note ThreefixedRGBcomponentsactingalongcannotgenerateallspectrumcolors Secondarycolors Magenta redplusblue Cyan greenplusblue Yellow redplusgreen PrimaryandSecondaryColors Distinguishcolors In1854 GrassmannpointedthatHVScanonlydistinguishthreevariationsofcolor BrightnessChromaticnotionofintensityHueThedominantwavelengthinamixtureoflightwavesDominantcolorasperceivedbyanobserver SaturationTherelativepurityortheamountofwhitelightmixedwithahue Tri stimulusValues Tri stimulusValuesTheamountsofred green andblueneededtoformanyparticularcolor AredenotedbyX Y Z respectively Tri chromaticCoefficientsBywhichacoloristhenspecified Isdefinedas ChromaticityDiagram TypicalColorGamut 6 2ColorModels MotivationTofacilitatethespecificationofcolorsinsomestandard generallyacceptedway NatureAspecificationofcoordinatesystemandasubspacewithinthatsystemwhereeachcolorisrepresentedbyasinglepoint Alsotermedofcolorspaceorcolorsystem Preface Mostcolormodelsinusetodayareorientedeithertowardhardware suchasforcolormonitorsandprinters ortowardapplicationswherecolormanipulationsisagoal suchascolorgraphics RGBmodelforcolormonitors abroadclassofcolorvideocamerasCMY cyan magenta yellow model CMYK black ColorprintingHSI hue saturation intensity Humandescribeandinterpretcolor 6 2 1TheRGBColorModel SomeConcepts PixeldepthThenumberofbitsusedtorepresenteachpixelinRGBspaceFull colorimageisusedoftentodenotea24 bitRGBcolorimage 28 3 16 777 216 Illustration SafeRGBcolors Whilehigh enddisplaycardsandmonitorsprovidea24 bitRGBimageManysystemsinusetodayarelimitedto256colors Asubsetofcolorsthatarelikelytobereproducedfaithfully reasonablyindependentlyofviewerhardwarecapabilities Fortyofthe256colorsareknowntobeprocesseddifferentlybyvariousdifferentsystems soremaining216colorsarecommon Eachofthe216safecolorscangetvalueonlybe0 51 102 153 204 or255 216SafeRGBColors TheRGBSafe colorCube 6 2 2TheCMYandCMYKModels CMYTheprimarycolorsofpigments Cyan magenta andyellow RGBtoCMYconversionCMYKInsteadofaddingC M andYtoproduceblack afourthcolorblackisadded TheDrawbackofRGB CMYModels Thesecolorsystemsareideallysuitedforhardwareimplementations Notwellsuitedfordescribingcolorsforhumaninterpretation Example onedoesnotrefertothecolorofanautomobilebygivingthepercentageofeachoftheprimariescomposingitscolor Furthermore wedonotthinkofcolorimageasthecompositionofthreeprimaryimages 6 2 3TheHISColorModel Humandescribescolorintermsofhuesaturationandbrightness Hue describethepurecolor pureyellow orange greenorred Saturationmeasuresthedegreetowhichapurecolorisdilutedbywhitelight Brightnessisasubjectivedescriptordifficulttobemeasured RelationshipbetweenRGBandHSI Allpointescontainedintheplanesegmentdefinebytheintensityandboundaryofthecubehavethesamehue HueandSaturation TheHSIColorModel ConvertingColorsfromRGBtoHSI ConvertingColorsfromHIStoRGB ConvertingColorsfromRGBtoHSI Example ManipulatingHISComponentImages ManipulatingHISComponentImages 6 3Pseudo colorImageProcessing MotivationHumanscandiscernthousandsofcolorshadesandintensities comparedtoaboutonlytwodozenshadesofgray TheprincipaluseisforhumanvisualizationandInterpretationofgray scaleeventsinanimageorsequenceofimages Pseudo false ColorImageProcessingAssigningcolorstomonochromeimagesB