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1、第5期電子學報Vol.34No.52006年5月ACTAELECTRONICASINICAMay2006保持圖像亮度的局部直方圖均衡算法1,2111江巨浪,張佑生,薛峰,胡敏(1.合肥工業(yè)大學計算機與信息學院,安徽合肥230009;2.安慶師范學院物理與電氣工程學院,安徽安慶246011)摘要:現(xiàn)有的局部直方圖均衡算法用于圖像的對比度增強時,輸出圖像的亮度與輸入圖像無關.由于圖像增強的很多實際應用需要保持原始圖像的亮度,為此提出一種新的局部直方圖均衡算法.以子塊部分重疊的局部直方圖均衡算法(POSHE)為基礎,改進其對子塊圖像的均衡方式:根據(jù)亮度均值對子塊圖像進行遞歸分解,得到一系列
2、不同灰度范圍的子圖像,然后對每一個子圖像在其相應的灰度范圍內(nèi)進行直方圖均衡,最后合并這些子圖像的均衡結果.實驗結果表明,這種局部直方圖均衡新算法既能充分增強圖像局部細節(jié),又能保持輸入圖像的亮度,且亮度的保持程度可由用戶進行控制.本文算法使所增強的圖像具有更加自然的視覺效果,能更好地滿足消費類電子工業(yè)對圖像對比度增強的應用要求.關鍵詞:對比度增強;直方圖均衡;局部直方圖均衡;亮度保持中圖分類號:TP391.41文獻標識碼:A文章編號:0372-2112(2006)05-0861-06LocalHistogramEgualizationwithBrightnessPreservation
3、1,2111JIANGJu-lang,ZHANGYou-sheng,XUEFeng,HUMin(1.SchoolofComputerScienceandInformation,hefeiUniversityofTechnology.hefei,Anhui230009,China;2.SchoolofPhysicsandElectricalEngineering,AngingTeacher'sCollege.Anging,Anhui246011,China)Abstract:Asthetraditionalalgorithmsforlocalhistogramegualizationi
4、susedtoenhancethecontrastofanim-age,theoutputbrightnessisalwaysregardlessoftheinputimage.However,thisisnotthedesirablepropertyinmanyap-plicationswherepreservingtheoriginalbrightnessisessential,soanewalgorithmoflocalhistogramegualizationispro-posed.Basedonthealgorithmofpartiallyoverlappedsub-blo
5、ckhistogramegualization(POSHE),wechangethewayofegualizingsub-block:basedonthemean,eachsub-blockisseparatedrecursivelyintoaseriesofsub-imageswithdifferentgrayranges,thenthehistogramsareegualizedovertheirrespectivegrayranges,andfinallytheoutputofthesub-blockiscomposedwiththeresultingegualizedsub-
6、images.Thesimulationresultsshowthat,withthenewalgorithm,thelocalde-tailsontheimagecanbeenhancedeffectively,andtheoriginalbrightnesscanalsobepreservedinthemeantime.Besides,scalabledegreeofbrightnesspreservationmaybeachievedbychoosingthenumberofrecursiveseparation.Theproposedalgorithmcanenhanceth
7、eimageinamorenaturalmannerandhence,isveryusefulformanycommercialpurposessuchasconsumerelectronicswherebrightnesspreservationisreguired.Keywords:contrastenhancement;histogramegualization;localhistogramegualization;brightnesspreserv