图片编码图片解码.doc

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1、USINGTHEIJGJPEGLIBRARYCopyright(C)1994-1996,ThomasG.Lane.ThisfileispartoftheIndependentJPEGGroup'ssoftware.Forconditionsofdistributionanduse,seetheaccompanyingREADMEfile.Thefileexample.cprovidesheavilycommentedskeletoncodeforcallingtheJPEGlibrary.Alsoseejpeglib.h

2、(theincludefiletobeusedbyapplicationprograms)forfulldetailsaboutdatastructuresandfunctionparameterlists.Thelibrarysourcecode,ofcourse,istheultimatereference.Notethattherehavebeen*major*changesfromtheapplicationinterfacepresentedbyIJGversion4andearlierversions.The

3、olddesignhadseveralinherentlimitations,andithadaccumulatedalotofcruftasweaddedfeatureswhiletryingtominimizeapplication-interfacechanges.Wehavesacrificedbackwardcompatibilityintheversion5rewrite,butwethinktheimprovementsjustifythis.TABLEOFCONTENTS-----------------

4、Overview:FunctionsprovidedbythelibraryOutlineoftypicalusageBasiclibraryusage:DataformatsCompressiondetailsDecompressiondetailsMechanicsofusage:includefiles,linking,etcAdvancedfeatures:CompressionparameterselectionDecompressionparameterselectionSpecialcolorspacesE

5、rrorhandlingCompresseddatahandling(sourceanddestinationmanagers)I/OsuspensionProgressiveJPEGsupportBuffered-imagemodeAbbreviateddatastreamsandmultipleimagesSpecialmarkersRaw(downsampled)imagedataReallyrawdata:DCTcoefficientsProgressmonitoringMemorymanagementLibra

6、rycompile-timeoptionsPortabilityconsiderationsNotesforMS-DOSimplementorsYoushouldreadatleasttheoverviewandbasicusagesectionsbeforetryingtoprogramwiththelibrary.Thesectionsonadvancedfeaturescanbereadifandwhenyouneedthem.OVERVIEW========Functionsprovidedbythelibrar

7、y---------------------------------ThelibraryincludesasubstantialamountofcodethatisnotcoveredbytheJPEGstandardbutisnecessaryfortypicalapplicationsofJPEG.ThesefunctionspreprocesstheimagebeforeJPEGcompressionorpostprocessitafterdecompression.Theyincludecolorspacecon

8、version,downsampling/upsampling,andcolorquantization.Theapplicationindirectlyselectsuseofthiscodebyspecifyingtheformatinwhichitwishestosupplyorreceiveimagedata