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ID:33105472
大小:8.79 MB
页数:35页
时间:2019-02-20
《改进的小波阈值去噪算法-研究》由会员上传分享,免费在线阅读,更多相关内容在行业资料-天天文库。
1、哈尔滨理工大学理学硕士学位论文TheStudyonImprovedWaveletThresholdDenoisingMethodAbstractWaveletthresholddenoisingmethodisasimpleandeffectivedenoisingmethod.buttosomeextent.therearesomedefectsonthetraditionalwaveletthresholdmethodinpracticalapplication.Therefore,itisquitenecessarytodothefurtherresearchonthewavelet
2、thresholdmethod.Thetraditionaluniversalthresholdisfixedoneachscaleanddoesnothavetheadaptivecapacity,whichhasagreatimpactonthedenoisingeffect.Thehardthresholdfunctionisdiscontinuousatthethresholdpoints,forthesoftthresholdfunction,althoughitiscontinuousatthethresholdpoints,thereexiststheconstantdevi
3、ationbetweenthesoftthresholdfunctionandtherealsignal.Thewavelettransformiseffectiveforthedetectionofpointsingularity,butitcannotdealwiththelinesingularityoftheimageeffectively.However,thisdrawbackofwavelettransformCanbecoveredbytheridgelettransform.Thelinesingularitycanbedetectedwellbytheridgelett
4、ransform.Toachievethepurposeofremovingthenoiseeffectively,thewaveletthresholdmethodisimprovedinthispaper.Thespecificworkisasfollows:Firstly,theuniversalthresholdisimprovedinthispaperSOthatitCanbechangedwiththedecompositionlevel.Comparedwithuniversalthreshold,theimprovedthresholdisflexibleandaccord
5、stothedistributionofnoiseineachlayer.Thenthethresholdfunctionisimprovedinthispaper,aparameterisaddedtotheimprovedthresholdfunction.Byadjustingtheparameter,theimprovedthresholdfunctioniSbetweenthetwothresholdfunctions.itcanovercomediscontinuityofthehardthresholdfunctionandreducethedeviationbetweent
6、hesoftthresholdfunctionandtherealsignal.Theimprovedthresholdfunctioniscontinuousanddifferentiable.Inthisway,itisratherconvenienttodosomesubsequentprocessing.Secondly.thewaveletthresholdmethodcannotdealwiththeline哈尔滨理工大学理学硕士学位论文singularityeffectively,buttheridgelettransformcouldmakeupthisshortcomin
7、g.Theimageshavegreat”wrap—around”effect,afterridgeletmethodhasbeenusedtoremovenoise,SOthetraditionalridgeletdenoisingmethodisimprovedinthispaper.Firstofall,noisyimageisdividedintoimageblockswhicharethesamesizeand
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