信號圖像處理課件：Chapter 1 Introduction

Chapter1Introduction1.1BasicConcept1.1.1WhatisanImage?photograph==Image?SampleofPhotographHumanbeingLena:mostfamouspictureinthefieldofDigitalImageProcessingSampleofPhotographsLandscapeSampleofPhotographsFlowerAnoil

paintingisanimage,butisNOTaphotographAmImageof3DModelWhatisanImageAnImagingSystemImageInput?WhatisaPhotograph?PhotoSceneImageof3DModelImagingSystem:3DRenderSoftwareInput:3DModelFileColorImageandgraylevelimage1.1.1WhatisanImage?(GrayLevel)Animagecanbedefineasatwo-dimensionalfunctionf(x,y),wherexandyarespatialcoordinates,andthevalueofamplitudeorvalueoffat(x,y)iscalltheintensityorgrayleveloffatthatpoint.MathematicalmodelofImageOriginXYLocation:(x,y)Value:f(x,y)WhatisanColorImagef(x,y)isavector,forexample,[r,g,b]T1.1.2WhatisaDigitalImageWhenx,y,intensityoffareallfinite,discretequantities,wecalltheimageasDigitalImage.

Becausethecoordinate(x,y)arediscrete,soadigitalimagecanbeconsideredasaMatrixora2Darray.Carte’siancoordinatesystem

GraphicsCoordinateSystem1.1.2WhatisaDigitalImageGrayleveldigitalimage:2-DbytearrayRangeofbyte:[minmax]Min:BlackMax:White[Programmingof“Hello,Image”][IntroductiontoC--]

1.1.3PixelPixelcanbeseetheelementofpictureorimage.Eachpixelhasaparticularlocation((x,y)coordinate)andvalue(intensityorcolor)[Programming:Howtoaccesspixel,readandwriteoperation]1.1.3Pixel1.1.3PixelA0A0A0A0A0A0A0A0A0A0A0A0A0A0A0A0A0A00000A0A0A0A00000A0A0A0A00000A0A0A0A00000A0A0A0A0A0A0A0A0A0A0A0A0A0A0A0A0A0A01.1.3Pixel1.1.4ImageResolutionLogicResolution,ImageSize:HowmanypixelsinaimageCameraSensorResolutionResolution:2megabytepixelsScreenResolutionVGAresolution:640X480HDresolution:1920X1080AspectRatioAspectRatio=width/height2megabytepixels=1600X12001.1.4ImageResolution[Programming:ImageSize](0,0)(1,0)(0,1)(1,1)(f.GetLegth(0)-1,0)(0,f.GetLegth(1)-1)(f.GetLength(0)-1,f.GetLength(1)-1)1.2WhatisDigitalImageProcessingDigitalimageprocessingmeansprocessingdigitalimagesbymeansofdigitalcomputers.ProcessingSystemoutputinputDigitalImageProcessingSystemOutput:g(x,y)or？Input:f(x,y)1.3ApplicationsofImageProcessing1.3.1LowLevelImageProcessingSpatialTransforms[Demoofsamepictureviewsoftware]ImageEnhancementTogetabetterimageImageRestorationTogetmore“real”image（9.30）1.3.2ImageCompressionWhyweneedthisTechnologyTheamountdataofimageorvideomaybeextremelyhuge1.3.2ImageCompressionTheamountdataof2hourofSDVideo.

SDmeansStandardDefinition,resolutionis720X480

tostorageapixelofcolorimageneed3bytes.

Oneseconddatais

720X480(resolution)X3X30(frames/sec)=31,104,000bytes

totalamountis31,104,000X3600(sec/h)X2=2.24X10topowerof11bytes

or224GB(gigabyte)1.3.2ImageCompression1.3.2ImageCompressionDataCompress：entropy

coding，losslesscompressionImageCompress：DCT，entropy

coding，ext,lossycompression1.3.3computervisionormachinevisionUsecomputerandimagesensortoemulatehumanvision

WhatisWhereWhatmeansrecognitionWheremeansSceneAnalysisor(SceneReconstruction)1.3.3computervision(Microsoft)computervision(Microsoft)computervision(Microsoft)computervision(Microsoft)ComputerVisionLow-levelProcessing:bothinputandoutputareimagesMid-levelProcessing:inputimages,outputattributesofthoseimagesImageSegmentationImageIndexing(FeatureExtraction)High-