数字图像处理-Color-Image-Processing

DigitalImageProcessingColorImageProcessing

(Chapter6)PreviewMotive

-Colorisapowerfuldescriptorthatoftensimplifiesobjectidentificationandextractionfromascene.-Humancandiscernthousandsofcolorshadesandintensities,comparedtoaboutonlytwodozenshadesofgray.H.R.PourrezaPreviewH.R.PourrezaPreviewPreviewColorimageprocessingisdivideintotwomajorarea:

Full-ColorProcessingPseudo-ColorProcessingColorFundamentalsTheexperimentofSirIsaacNewton,in1666.ColorFundamentals(con’t)cThecolorthathumanperceiveinanobject=thelightreflectedfromtheobjectIlluminationsourcescenereflectioneyeColorFundamentals(con’t)cBasicquantitiestodescribethequalityoflightsource:Radiance:Totalamountofenergythatflowsfromthelightsource(inW).Luminance:Ameasureoftheamountofenergyanobserverperceivesfromthelightsource(inlm)Brightness:Asubjectivedescriptorthatembodiestheachromaticnotionofintensityandispracticalimpossibletomeasure.ColorFundamentals(con’t)cColorFundamentals(con’t)StandardwavelengthvaluesfortheprimarycolorsColorFundamentals(con’t)ColorFundamentals(con’t)ThecharacteristicsgenerallyusedtodistinguishonecolorfromanotherareBrightness,

Hue,andSaturation.Hue:Representsdominantcolorasperceivebyanobserver.Saturation:RelativepurityortheamountofwhitelightmixedwithahueHueandsaturationtakentogetherarecalledChromaticity,andtherefore,acolormaybecharacterizedbyitsBrightnessandChromaticity.ColorFundamentals(con’t)Tri-stimulusvalues:TheamountofRed,GreenandBlueneededtoformanyparticularcolor Denotedby:X,YandZTri-chromaticcoefficient:ColorFundamentals(con’t)GreenPoint=62%green,25%red,13%blue.ChromaticityDiagramColorFundamentals(con’t)ColorGamutproducedbyRGBmonitorsColorGamutproducedbyhighqualitycolorprintingdeviceColorModelsThepurposeofacolormodel(alsocalledcolorspaceorcolorsystem)istofacilitatethespecificationofcolorsinsomestandard,generallyacceptway.RGB

(red,green,blue):monitor,videocamera.CMY(cyan,magenta,yellow),CMYK(CMY,black)modelforcolorprinting.andHSImodel,whichcorrespondscloselywiththewayhumansdescribeandinterpretcolor.TheRGBColorModelsTheRGBColorModels(con’t)TheRGBColorModels(con’t)TheRGBColorModels(con’t)SafeRGBColors(SafeWebcolors)TheRGBColorModels(con’t)TheCMYandCMYKColorModelsCyan,MagentaandYellowarethesecondarycolorsoflightMostdevicesthatdepositcoloredpigmentsonpaper,suchascolorprintersandcopiers,requireCMYdatainput.TheHSIColorModelsTheHSIColorModelsTheHSIColorModelsConvertingcolorsfromRGBtoHSITheHSIColorModelsConvertingcolorsfromHIStoRGBRGsector:TheHSIColorModelsConvertingcolorsfromHIStoRGBGBsector:TheHSIColorModelsConvertingcolorsfromHIStoRGBBRsector:TheHSIColorModelsTheHSIColorModelsTheHSIColorModelsRGBHSIHSIRGBPseudocolorImageProcessingPseudocolor(alsocalledfalsecolor)imageprocessingconsistsofassigningcolorstograyvaluesbasedonaspecifiedcriterion.Theprincipaluseofpseudocolorisforhumanvisualizationandinterpretationofgray-scaleeventsinanimageorsequenceofimages.IntensitySlicingIntensitySlicing(con’t)IntensitySlicing(con’t)IntensitySlicing(con’t)GrayLeveltoColorTransformationsGrayLeveltoColorTransformationsGrayLeveltoColorTransformationsGrayLeveltoColorTransformationsGrayLeveltoColorTransformationsH.R.PourrezaGrayLeveltoColorTransformationsLetcrepresentanarbitraryvectorinRGBcolorspaceForanimageofsizeM*N,BasicofFullColorImageProcessingBasicofFullColorImageProcessingMajorcategoriesoffull-colorImageprocessing:Per-color-componentprocessingVector-basedprocessingBasicofFull-ColorImageProcessingBasicofFull-ColorImageProcessing

ColorTransformationProcessingthecomponentsofacolorimagewithinthecontextofasinglecolormodel.ColorcomponentsoffColorcomponentsofgColormappingfunctionsFull-ColorImageProcessing

ColorTransformationCMYKRGBHSISomedifficultyininterpretingtheHUE:Discontinuitywhere0and360ºmeet.Hueisundefinedforasaturation0Full-ColorImageProcessing

ColorTransformation:ModifytheIntensityFull-ColorImageProcessing

ColorTransformation:ColorComplementFull-ColorImageProcessing

ColorTransformation:ColorComplementFull-ColorImageProcessing

ColorTransformation:ColorSlicingMotive:HighlightingaspecificrangeofcolorsinanimageBasicIdea:DisplaythecolorofinterestsothattheystandoutfrombackgroundUsetheregiondefinedbythecolorsasamaskforfurtherprocessingFull-ColorImageProcessing

ColorTransformation:ColorSlicing1.Colorsofinterestareenclosedbycube(orhypercubeforn>3)2.ColorsofinterestareenclosedbySphereFull-ColorImageProcessing

ColorTransformation:ColorSlicingCubeSphereFull-ColorImageProcessing

ColorTransformation:ToneandColorCorrectionTheColorsofmonitorshouldrepresentaccuratelyanydigitallyscannedsourceimages,aswellasthefinalprintedoutInconjunctionwithdigitalcameras,flatbedscanners,andinkjetprinters,theyturnapersonalcomputerintoadigitalDarkroomDeviceIndependentColorModelTheModelofchoiceformanycolormanagementsystem(CMS)is

CIEL*a*b*(alsocalledCIELAB)modelFull-ColorImageProcessing

ColorTransformation:ToneandColorCorrectionL*a*bColorComponents:XW,YWandZWarereferencewhitetristimulusvalues(definedbyx=0.3127andy=0.3290inthechromaticitydiagramFull-ColorImageProcessing

ColorTransformation:ToneandColorCorrectionThetonalrangofanimage,alsocalleditskey-type,referstoitsgeneraldistributionofcolorintensities.

High-keyimages:Mostoftheinformationisconcentratedathighintensities.

Low-keyimages:Mostoftheinformationisconcentratedatlowintensities.Full-ColorImageProcessing

ColorTransformation:TonalCorrectionMiddle-keyImageFull-ColorImageProcessing

ColorTransformation:TonalCorrectionHigh-keyImageFull-ColorImageProcessing

ColorTransformation:TonalCorrectionLow-keyImageFull-ColorImageProcessing

ColorTransformation:ColorCorrectionTheproportionofanycolorcanbeincreasedbydecreasingtheamountoftheopposite(orcomplementary)colorintheimageorbyraisingtheproportionofthetwoimmediatelyadjacentcolorsordecreasingthepercentageofthetwocolorsadjacenttothecomplement.Magenta

RemovingRedandBlueAddingGreenFull-ColorImageProcessing

ColorTransformation:ColorCorrectionFull-ColorImageProcessing

ColorTransformation:HistogramProcessingHistogramEqualizingtheIntensitySaturationAdjustmentFull-ColorImageProcessing

ColorImageSmoothingAveraging:Full-ColorImageProcessing

ColorImageSmoothingRedBlueGreenFull-ColorImageProcessing

ColorImageSmoothingHueSaturationIntensityFull-ColorImageProcessing

ColorImageSmoothingAveragingR,GandBAveragingIntensityDifference

Full-ColorImageProcessing

ColorImageSharpeningTheLaplacianofVectorc:Full-ColorImageProcessing

ColorImageSharpeningSharpeningR,GandBSharpeningIntensityDifference

Full-ColorImageProcessing

ColorSegmentationSegmentationisaprocessthatpartitionsanimageintoregionsSegmentationinHISColorSpaceSegmentationinRGBVectorSpaceColorEdgeDetectionH.R.PourrezaFull-ColorImageProcessing

ColorSegmentation:inHISColorSpa