毕业设计论文外文翻译-jpeg标准研究及算法实现Word文档格式.doc

毕业设计论文外文翻译-jpeg标准研究及算法实现Word文档格式.doc

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学生姓名

专业班级电子信息07级1班

学号

院（系）计算机与通信工程学院

指导教师

完成时间2011年4月10日

英文原文

JPEG2000imagecompressionstandard

andcharacteristics

Abstract

Withthedevelopmentofthenetworkandmultimediatechnologies,peopleneedmoreandmoreimageswithhighfunctionandquantity,sothecompressiveimagetechniquesrequirehigherperformanceaswellasnewcharacteristicstosatisfysomespecialuse.Forthis,ISOreleasedagainanewstaticimagecompresstechnique-JPEG2000,whichmaybecomethenewimagecompressionstandardinthefuture.

JPEG2000istoadapttothecontinuousdevelopmentofimagecompressionapplications,theemergenceofnewstillimagecompressionstandard.JPEG2000imagecodingsystemdescribestherealizationoftheprocess,ofwhichthebasicalgorithmusedisdescribedandkeytechnologies,introducedthenewstandardfeaturesandapplications,anditsperformanceisanalyzed.Withtherapidgrowthofmultimediaapplicationsandnetworkscontinuestodevelop,thetraditionalJPEGcompressiontechnologyhasbeenunabletomeetthepeople'

sdigitalmultimediaimagedatarequirements,amorepowerfulandefficientsuperiorstillimagecompressionstandardhasbeenreferredtothedevelopmentagenda,thisisaJPEG2000.

1.Introduction

JPEG（JointPhotographicExpertsGroup）istheInternationalOrganizationforStandardization（ISO）developedundertheleadershipofthecommitteestillimagecompressionstandard,thefirstsetofinternationalstillimagecompressionstandardISO10918-1（JPEG）isthatestablishedbytheCommittee.AstheexcellentqualityJPEG,sothatwithinafewyearshewasagreatsuccess,iswidelyusedinthefieldofInternetanddigitalcamerasonthesite80%haveadoptedtheJPEGimagecompressionstandard.However,thecurrentJPEGstillimagecompressionstandard,withmid-rangeandhigh-bit-rateontheratedistortioncharacteristicsofagood,butinthecontextoflowbitrate,therewillbeobviousblockingeffects,itsqualityhasbecomeunacceptable.JPEGcannotbeprovidedinasinglestreamlossyandlosslesscompression,andcannotsupportmorethan64×

64Koftheimagecompression.Atthesametime,despitethecurrentJPEGstandardhasarequirementtorestarttheinterval,butwhenbiterrorsencounteredwhentheimagequalitywillbeseriouslydamaged.Tosolvetheseproblems,sinceMarch1997onwards,JPEGimagecompressionstandardscommitteestartedtodevelopanewgenerationofimagecompressionstandardtoaddresstheseproblems.InMarch2000theTokyoconferencetoidentifyanewgenerationofcolorstillimagecodingstandardJPEG2000imagecompressioncodingalgorithm.

2.JPEG2000imagecompressionstandardprofile

JPEG2000systemisdividedintothefollowingsevenparts:



①JPEG2000imagecodingsystem

②Expansion（tothecoreofthedefinition①addmorefeaturesandsophistication）;

③movementJPEG2000;

④consistency;

⑤referencesoftware（nowincludesJavaandCimplementation）;

⑥compoundimagefileformat（fordocumentscanningandfaxapplications）;

⑦oftheminimumsupportto①（technicalreport）.

①asfullyaccreditedISOstandardthatdefinesthecorecompressionandminimumfileformats,②~⑥definitionofcompressionandexpansionoffileformats.Which,①hasbeenfinalized,andotherarestillinprocess.DiscussedinthisarticleisbasedontheJPEG2000standardPart1.

Intheencoder,firstlythesourceimagesoftheresultofthepre-treatment,todealwiththeresultsofdiscretewavelettransform,waveletcoefficientsobtained.Thenthewaveletcoefficientswerequantizativedandentropycoding,thefinalcompositionofthestandardoutputcodestream（bitstream）.Decodersareencoderreverseprocess,Firsttocodeflowunpackandentropydecoding,andthenreversetoquantifyanddiscretewaveletinversetransform,inversetransformtheresultsofthepost-processingsynthesis,wehavereconstructedimagedata.AlthoughJPEG2000andJPEGencodinganddecodingprocessissimilar,thereisaverybigdifferencebetweenthetheconcreterealizationofeachstep.Thegeneralstepsintheencodingprocessisasfollows:

（1）composedofmorethanonecolorcomponentimageisdecomposedintoasinglecolorcomponentimage.Therearecertaincorrelationbetweenweightbydecompositionrelatedcomponents,throughthedecompositionoftherelevantcomponentstransformcanreducetheredundancybetweenthedatatoimprovecompressionefficiency;

（2）componentsoftheimageisdecomposedintoarectanglethesizeofaunifiedpiece-theimagechip.Imagefilmistransformed,andthebasicunitofencodinganddecoding;

（3）Everyimagepieceforwavelettransform.Generatemulti-levelfactorimage.Thecoefficientsofthesedifferentseries,differentimagescanbereconstructedresolutionimages;

（4）theresultsofmulti-leveldecompositionofwaveletcoefficientsiscomposedofmultiplesub-band.Theysaidthatthefilmimagelocalarea（ratherthanthewholeimage）ofthefrequencycharacteristics;

（5）sub-bandcoefficientstoquantify,andthecompositionofarectangulararrayof"

codeblock"

;

（6）ofacodeblockinthecoefficientbitplanes（acodeblockinthecoefficientvalueshavethesamerighttothosebits）forentropycoding;

（7）relativetothebackgroundoftheimageareacanbecarriedouthigher-qualityregionofinterestcoding;

（8）throughthereignstreambyaddingmasktoincreasetheanti-interference;

（9）eachstreamhasoneofthemostanteriorheadstructure,itdescribesthepropertiesofthesourceimage,variousdecompositionandcodingstyle.Theheadstructurecanbeusedtolocate,extract,decodeandreconstructimages,imagescanbeobtainedwiththedesiredresolution,reproducibleprecision,areaofinterestorotherfeatures.

Encodingprocessismainlydividedintothefollowingprocesses:

pre-processing,coreprocessingandbit-streamorganization.Theimagepreprocessingpartincludesimagesegmentation,DClevel（DC）displacementandweightchange.Keyprocessinginpartbythediscretewavelettransform,quantizationandentropycodingform.Bit-streampartoftheorganizationincludezoning,codeblocks,layersandpackagesorganization.

3.ComparisonbetweenJPEGandJPEG2000

JPEG2000offersnumerousadvantagesovertheoldJPEGstandard,.OnemainadvantageisthatJPEG2000offersbothlossyandlosslesscompressioninthesamefilestream,whileJPEGusuallyonlyutilizeslossycompression4.JPEGdoeshavealosslesscompressionengine,butitisseparatefromthelossyengine,andisnotusedveryoften.Thus,whenhighqualityisaconcern,JPEG2000provestobeamuchbettercompressiontool.Becauseofthewaythecompressionengineworks,JPEG2000promisesahigherqualityfinalimage,evenwhenusinglossycompression.SincetheJPEG2000formatincludesmuchrichercontentthanexistingJPEGfiles,thebottomlineeffectistheabilitytodelivermuchsmallerfilesthatstillcontainthesamelevelofdetailasthelargeroriginalJPEGfiles.TheJPEG2000filescanalsohandleupto256channelsofinformationascomparedtothecurrentJPEGstandard,which,byreasonofcommonimplementation,islimitedtoonlyRGB（red,green,andblue）data.Figure1showstwoimagesthatwerefirstcompressedwiththeoldJPEGcompressionengine,andthencompressedusingtheJPEG2000method.TheimagesthatwerecompressedusingJPEG2000areseenfromFigure1toretainamuchhigherquality.

Figure1ComparisonoftwoimagescompressedusingJPEGandJPEG2000

AsecondadvantageofJPEG2000overJPEGisthatJPEG2000isabletoofferhighercompressionratiosforlossycompression.Forlossycompression,datahasshownthatJPEG2000cantypicallycompressimagesfrom20%-200%morethanJPEG.Compressionefficiencyforlossycompressionistypicallymeasuredusingthepeaksignaltonoiseratio,orPSNR,andtherootmeansquareerror（RMSE）.Thismethodseekstotakeintoaccountthevisualqualityretainedbythecompressionmethod,aswellashowmuchtheimagewascompressed.TheformulaforthePSNRcompressionefficiency,indB,isshownin

（1）,wherebisthebitdepthoftheoriginalimage.

AnexampleofsomePSNRefficienciesforJPEG2000andJPEGisshowninTable1.Twodifferentcolorimageswerecompressedusingseveraldifferentbitrates（measuredinbitsperbpp）usingbothJPEG2000andJPEG.Ahigherbitratewillresultinahigherqualitypicture.TheanalysiswasperformedbyMarylineCharrier,DiegoSantaCruz,andMathiasLarssonaspartofanoverviewofJPEG2000.TheresultsindicatethatJPEG2000consistentlyoffersahighercompressionefficiency.OneshouldnotethatsincethePSNRismeasuredonalogscale,thedatainTable1indicatesthatinactualitythetestshowedthatJPEG2000compressesalmosttwicemorethanJPEG.

Table1ComparisonofPSNRcompressionefficiencies（indB）

fortwoimagesatvariousbitrates

JPEG2000isalsoabletooffercompressionratiosofabout2.5:

1forlosslesscompression,whereasJPEGwasnotabletosatisfactorilyperformlosslesscompressionatall.Losslesscompressionratiosaresimplymeasuredbyhowmuchlessmemorythecompressedimageuses.

AnotheradvantageofJPEG2000isitsabilitytodisplayimagesatdifferentresolutionsandsizesfromthesameimagefile.WithJPEG,animagefilewasonlyabletobedisplayedasingleway,withacertainresolution.BecauseJPE