資源描述：
《數字圖像處理,岡薩雷斯,課件英文版Chapter08圖像壓縮.ppt》由會員上傳分享，免費在線閱讀，更多相關內容在PPT專區(qū)-天天文庫。
1、DigitalImageProcessingChapter8:ImageCompression11August2006DatavsInformationInformation=Matter(????)Data=ThemeansbywhichinformationisconveyedReducingtheamountofdatarequiredtorepresentadigitalimagewhilekeepinginformationasmuchaspossibleImageCompressionRelativeDataRedundancyandCompressio
2、nRatioRelativeDataRedundancyCompressionRatioTypesofdataredundancy1.Codingredundancy2.Interpixelredundancy3.PsychovisualredundancyCodingRedundancyDifferentcodingmethodsyielddifferentamountofdataneededtorepresentthesameinformation.ExampleofCodingRedundancy:VariableLengthCodingvs.FixedLen
3、gthCodingLavg3bits/symbolLavg2.7bits/symbol(ImagesfromRafaelC.GonzalezandRichardE.Wood,DigitalImageProcessing,2ndEdition.VariableLengthCodingConcept:assignthelongestcodewordtothesymbolwiththeleastprobabilityofoccurrence.(ImagesfromRafaelC.GonzalezandRichardE.Wood,DigitalImageProcessing
4、,2ndEdition.InterpixelRedundancyInterpixelredundancy:Partsofanimagearehighlycorrelated.Inotherwords,wecanpredictagivenpixelfromitsneighbor.(ImagesfromRafaelC.GonzalezandRichardE.Wood,DigitalImageProcessing,2ndEdition.RunLengthCodingThegrayscaleimageofsize343x1024pixelsBinaryimage=343x1
5、024x1=351232bitsLineNo.100RunlengthcodingLine100:(1,63)(0,87)(1,37)(0,5)(1,4)(0,556)(1,62)(0,210)Total12166runs,eachrunuse11bits?Total=133826Bits(ImagesfromRafaelC.GonzalezandRichardE.Wood,DigitalImageProcessing,2ndEdition.PsychovisualRedundancyTheeyedoesnotresponsewithequalsensitivity
6、toallvisualinformation.8-bitgrayscaleimage4-bitgrayscaleimage4-bitIGSimageFalsecontours(ImagesfromRafaelC.GonzalezandRichardE.Wood,DigitalImageProcessing,2ndEdition.ImprovedGrayScaleQuantizationPixeli-1ii+1i+2i+3GraylevelN/A01101100100010111000011111110100Sum000000000110110010010111100
7、0111011110100IGSCodeN/A0110100110001111+Algorithm1.Addtheleastsignificant4bitsofthepreviousvalueofSumtothe8-bitcurrentpixel.Ifthemostsignificant4bitofthepixelis1111thenadd0000instead.KeeptheresultinSum2.Keeponlythemostsignificant4bitsofSumforIGScode.FidelityCriteria:howgoodisthecompr
