基于小波变换的雾天图像增强方法

282Vol.28No．220112ComputerApplicationsandSoftwareFeb．20113002222009－10－22。08JCYBJC12100。。、。。FOGGYDAYIMAGEENHANCEMENTMETHODBASEDONWAVELETTRANSFORMMaYunfeiHeWenzhangSchoolofScienceTianjinUniversityofTechnologyandEducationTianjin300222ChinaAbstractInthispaperthethresholddeterminationmodelandthedefogthresholdfunctionoffoggydayimageareproposedinlightofthefeatureofimagestakeninhazeweatherwithlowcontrastandlowvisibility．Basedonthatanewenhancementmethodforfoggydayimagesbasedonwavelettransformispresentedaswell．Experimentalresultsshowthatthefoggydayimagesprocessedbythemethodinthispaperhavebettercontrastandhigherdegreeofclaritytheirvisualeffectisnoticeablymelioratedwithmuchlowimagedistortion．KeywordsDegradationmodelImageenhancementWavelettransformImageenhancementThresholdfunction0、、。1～6。。。。2080。。。。1。。4。。WTfab1b2=＜fx1x2ψab1b2x1x2＞=1afx1x2ψx1－b1ax2－b2()adx1dx2fx1x2=1cψ∫+∞0daa3WTfab1b2ψx1－b1ax2－b2()adb1db2ψab1b2x1x2ψx1x2722011ψab1b2x1x2=1aψx1－b1ax2－b2()a2。T·。。。。2．1。。gxy=fxy+nxyfxygxynxy。。。matlabthr=maxIthrI。、。。。CthrI=CI－a·thrCI＜－thra·CI|CI|≤thrCI+a·thrCI{＞thrCICthrICIaa=T槡thrT≥1T=2T。2．2。。。2．31n2345。3、、matlabR2008a。sym4a=2槡thr256。1a1b1c1d1e。1f。195295K1KM－24。1。14N=2MM－2、2M－2M－2、M－2、M－1。2222M－122+23+…+2M－1=2M－42M－4+M－2=2M+M－6M－2M－1。1M=1N。1N+N/2+N/4+…+2=2M+1－2NNN。23。。。。5FFT。—2—2XKXK。N=220。1．J．2001213204-206．2．FFTJ．200426262-64．3．M．2．2001．724。。“”。。。1NicolasHautiereDidierAubert．ContrastrestorationoffoggyimagesthroughuseofanonboardcameraJ．Proceedingofthe8thinterna-tionalIEEEconferenceonintelligenttransportationsystems20059601-606．2SrinivasaGNarasimhanShreeKNayar．Contrastrestorationofweath-erdegradedimagesJ．IEEETransactionsonpatternanalysisandmachineintelligence2003256713-724．3InampudRBPurimetlaTNSatyanarayanaPG．contrastdegradationforimprovingqualityofanimageJ．GeoscienceandRemoteSensingSymposium200263408-3410．4SrinivasaGNarasimhanShreeKNayar．RemovingweathereffectsfrommonochromeimagesJ．IEEEComputerSocietyConferenceonComputerVisionandPatternRecognition20012186-193．5SchechnerYYNarasimhanSGNayarSK．InstantdehazingofimagesusingpolaritionJ．IEEEcomputersocietyconferenceoncomputervisionandpatternrecognition20011325-332．6SrinivasaGNasasimhanShreeKNayar．Sheddinglightontheweath-erJ．Proceedingsofthe2003IEEEcomputersocietyconferenceoncomputervisionandpatternrecognition20031665-672．