IMPA Monographs Jonas Gomes Luiz Velho From Fourier Analysis to Wavelets Instituto de Matemática Pura e Aplicada IMPA Monographs Volume 3 This series, jointly established by IMPA and Springer,publishes advanced mono- graphsgivingauthoritativeaccountsofcurrentresearchinanyfieldofmathematics, with emphasis on those fields that are closer to the areas currently supported at IMPA.Theseriesgiveswell-writtenpresentationsofthe“state-of-the-art”infields ofmathematicalresearchandpointerstofuturedirectionsofresearch. SeriesEditors EmanuelCarneiro,InstitutodeMatemáticaPuraeAplicada SeverinoCollier,UniversidadeFederaldoRiodeJaneiro ClaudioLandim,InstitutodeMatemáticaPuraeAplicada PauloSad,InstitutodeMatemáticaPuraeAplicada Moreinformationaboutthisseriesathttp://www.springer.com/series/13501 Jonas Gomes • Luiz Velho From Fourier Analysis to Wavelets 123 JonasGomes LuizVelho BOZANOInvestimentos InstitutodeMatemáticaPuraeAplicada OfficesShoppingLeblon RiodeJaneiro,Brazil RiodeJaneiro,Brazil IMPAMonographs ISBN978-3-319-22074-1 ISBN978-3-319-22075-8 (eBook) DOI10.1007/978-3-319-22075-8 LibraryofCongressControlNumber:2015945959 MathematicsSubjectClassification(2010):42-XX,42C40,65-XX,65T60 SpringerChamHeidelbergNewYorkDordrechtLondon ©SpringerInternationalPublishingSwitzerland2015 Thisworkissubjecttocopyright.AllrightsarereservedbythePublisher,whetherthewholeorpartof thematerialisconcerned,specificallytherightsoftranslation,reprinting,reuseofillustrations,recitation, broadcasting,reproductiononmicrofilmsorinanyotherphysicalway,andtransmissionorinformation storageandretrieval,electronicadaptation,computersoftware,orbysimilarordissimilarmethodology nowknownorhereafterdeveloped. Theuseofgeneraldescriptivenames,registerednames,trademarks,servicemarks,etc.inthispublication doesnotimply,evenintheabsenceofaspecificstatement,thatsuchnamesareexemptfromtherelevant protectivelawsandregulationsandthereforefreeforgeneraluse. Thepublisher,theauthorsandtheeditorsaresafetoassumethattheadviceandinformationinthisbook arebelievedtobetrueandaccurateatthedateofpublication.Neitherthepublishernortheauthorsor theeditorsgiveawarranty,expressorimplied,withrespecttothematerialcontainedhereinorforany errorsoromissionsthatmayhavebeenmade. Printedonacid-freepaper SpringerInternational PublishingAGSwitzerlandispartofSpringerScience+Business Media(www. springer.com) To myfamily,thetrueforcethatpropelledmy carrier. —JonasGomes To mybeloveddaughterAliceVelho ChekrounandmygrandsonLevi Yitzchak Chekroun — LuizVelho. Preface From a digital viewpoint, most real-world applications can be reduced to the problem of function representation and reconstruction. These two problems are closelyrelatedtosynthesisandanalysisoffunctions.TheFouriertransformisthe classical tool used to solve them. More recently, wavelets have entered the arena providingmorerobustandflexiblesolutionstodiscretizeandreconstructfunctions. Starting from Fourier analysis, the course guides the audience to acquire an understandingof the basic ideas and techniques behind the wavelets. We start by introducing the basic concepts of function spaces and operators, both from the continuousanddiscreteviewpoints.WeintroducetheFourierandWindowFourier Transform,theclassicaltoolsforfunctionanalysisinthefrequencydomain,andwe usethemasaguidetoarriveattheWavelettransform.Thefundamentalaspectsof multiresolutionrepresentationand its importanceto functiondiscretization and to theconstructionofwaveletsarealsodiscussed. Emphasiswillbegivenonideasandintuition,avoidingmostofthemathematical machinery,whichareusuallyinvolvedinthestudyofwavelets.Becauseofthis,the bookdemandsfromthereadersonlyabasicknowledgeoflinearalgebra,calculus, andsomefamiliaritywithcomplexanalysis.Basicknowledgeofsignalandimage processingwouldbedesirable. This monographoriginated from the course notes of a very successful tutorial given by the authors during the years of 1998 and 1999 at ACM SIGGRAPH - theInternationalConferenceandExhibitiononComputerGraphicsandInteractive Techniques. ThenotesinEnglishfortheSIGGRAPHcoursehavebeenbasedonasetofnotes in Portuguese that we wrote for a wavelet course on the Brazilian Mathematical Colloquiumin1997atIMPA,RiodeJaneiro.WewishtothankSiomeGoldenstein whocollaboratedwithustoproducethePortuguesenotes. RiodeJaneiro,Brazil JonasGomes May2015 LuizVelho vii Contents 1 Introduction ................................................................ 1 1.1 ComputationalMathematics......................................... 1 1.1.1 AbstractionLevels.......................................... 2 1.2 RelationBetweentheAbstractionLevels........................... 4 1.3 FunctionsandComputationalMathematics......................... 6 1.3.1 RepresentationandReconstructionofFunctions ......... 6 1.3.2 SpecificationofFunctions.................................. 7 1.4 WhatistheRelationwithGraphics?................................ 7 1.4.1 DescriptionofGraphicalObjects.......................... 8 1.5 WheredoWaveletsFit?.............................................. 9 1.5.1 FunctionRepresentationUsingWavelets.................. 9 1.5.2 MultiresolutionRepresentation............................ 10 1.6 AbouttheseBook .................................................... 10 1.7 CommentsandReferences........................................... 11 2 FunctionRepresentationandReconstruction .......................... 13 2.1 RepresentingFunctions.............................................. 13 2.1.1 TheRepresentationOperator............................... 14 2.2 BasisRepresentation................................................. 15 2.2.1 CompleteOrthonormalRepresentation.................... 15 2.3 RepresentationbyFrames ........................................... 16 2.4 RieszBasisRepresentation.......................................... 18 2.5 RepresentationbyProjection........................................ 19 2.6 GalerkinRepresentation ............................................. 20 2.7 Reconstruction,PointSamplingandInterpolation ................. 21 2.7.1 PiecewiseConstantReconstruction........................ 21 2.7.2 PiecewiseLinearReconstruction .......................... 22 2.8 MultiresolutionRepresentation...................................... 23 2.9 RepresentationbyDictionaries...................................... 25 ix