DIP_Lecture_10

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1、ShanghaiJiaoTongUniversityInstituteofImageCommunication&InformationProcessingSchoolofElectronicInformation&ElectricalEngineeringDept.ofElectronicEngineering2010ShanghaiJiaoTongUniversityInstituteofImageCommunication&InformationProcessingSchoolofElectronicInformation&ElectricalEngineeringDept.ofElec

2、tronicEngineering2010DigitalImageProcessingIntroductionofImageCompressionTheoreticalFundamentalsofImageCompressionEntropyCodingPredictiveCodingTransformCodingWaveletCodingImageCompressionStandards2010DigitalImageProcessingIntroductionofImageCompressionTheoreticalFundamentalsofImageCompressionEntrop

3、yCodingPredictiveCodingTransformCodingWaveletCodingImageCompressionStandards2010DigitalImageProcessingSourceEncoder&Decoder2010DigitalImageProcessingTransformCoding2010DigitalImageProcessing•Areversible,lineartransformisusedtomaptheimageintoasetoftransformcoefficients,whicharethenquantizedandcoded•

4、Formostnaturalimages,asignificantnumberofthecoefficientshavesmallmagnitudesandcanbecoarselyquantized(ordiscardedentirely)withlittleimagedistortion•Encoder-subimagedecomposition-transformation-quantization-coding2010DigitalImageProcessing•Transformselection-DCT-DWT-WHT•Subimagesizeselection-8×8,16×1

5、6-toosmall&toobig•Coefficientsselection-regionsampling-thresholdsampling-adaptivesampling•Bitallocation-theoverallprocessoftruncating,quantizing,andcodingthecoefficientsofatransformedsubimage2010DigitalImageProcessingIntroductionofImageCompressionTheoreticalFundamentalsofImageCompressionEntropyCodi

6、ngPredictiveCodingTransformCodingWaveletCodingImageCompressionStandards2010DigitalImageProcessingWaveletCoding•Basicideas-Thecoefficientsofawavelettransformthatdecorrelatesthepixelsofanimagecanbecodedmoreefficientlythantheoriginalpixelsthemselves-Wavelettransform’sbasisfunctionscanpackmostoftheimpo

7、rtantvisualinformationintoasmallnumberofcoefficients,theremainingcoefficientscanbequantizedcoarselyortruncatedto0withlittleimagedistortion2010DigitalImageProcessingIntroductionofImageCompressionTheoreticalF