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1、图形图像处理信息与计算科学系张宝雷上节内容回顾小波分析简史小波与小波变换小波分析工具箱小波变换DWTDWTSingle-leveldiscrete1-Dwavelettransform.DWTperformsasingle-level1-Dwaveletdecompositionwithrespecttoeitheraparticularwavelet('wname',seeWFILTERSformoreinformation)orparticularwaveletfilters(Lo_DandHi_D)thatyouspecify.小波变换DWT
2、[CA,CD]=DWT(X,'wname')computestheapproximationcoefficientsvectorCAanddetailcoefficientsvectorCD,obtainedbyawaveletdecompositionofthevectorX.'wname'isastringcontainingthewaveletname.小波变换DWT[CA,CD]=DWT(X,Lo_D,Hi_D)computesthewaveletdecompositionasabovegiventhesefiltersasinput:Lo
3、_Disthedecompositionlow-passfilter.Hi_Disthedecompositionhigh-passfilter.Lo_DandHi_Dmustbethesamelength.DWTLetLX=length(X)andLF=thelengthoffilters;thenlength(CA)=length(CD)=LAwhereLA=CEIL(LX/2),iftheDWTextensionmodeissettoperiodization.LA=FLOOR((LX+LF-1)/2)fortheotherextension
4、modes.Forthedifferentsignalextensionmodes,seeDWTMODE.[CA,CD]=DWT(...,'mode',MODE)computesthewaveletdecompositionwiththeextensionmodeMODEyouspecify.MODEisastringcontainingtheextensionmode.DWT示例>>x=[11001100];[ca,cd]=dwt(x,'db1','mode','sym')ca=1.414201.41420cd=0000DWT示例>>x=[101
5、01010];>>[ca,cd]=dwt(x,'haar','mode','sym')ca=0.70710.70710.70710.7071cd=0.70710.70710.70710.7071DWT示例[F1,F2]=WFILTERS('haar','l')F1=0.70710.7071F2=0.70710.7071WFILTERSWFILTERSWaveletfilters.[LO_D,HI_D,LO_R,HI_R]=WFILTERS('wname')computesfourfiltersassociatedwiththeorthogonalo
6、rbiorthogonalwaveletnamedinthestring'wname'.Thefouroutputfiltersare:LO_D,thedecompositionlow-passfilterHI_D,thedecompositionhigh-passfilterLO_R,thereconstructionlow-passfilterHI_R,thereconstructionhigh-passfilterWFILTERSAvailablewaveletnames'wname'are:Daubechies:'db1'or'haar',
7、'db2',...,'db45'Coiflets:'coif1',...,'coif5'Symlets:'sym2',...,'sym8',...,'sym45'DiscreteMeyerwavelet:'dmey'Biorthogonal:'bior1.1','bior1.3','bior1.5''bior2.2','bior2.4','bior2.6','bior2.8''bior3.1','bior3.3','bior3.5','bior3.7''bior3.9','bior4.4','bior5.5','bior6.8'.ReverseBi
8、orthogonal:'rbio1.1','rbio1.3','rbio1.5''rbio2.2','rbio2.4','
