介绍image compression图像压缩.pdf
Althoughstillimagecompressionisatechniquedevelopedlongtimeago,andthereare
severalapproachwhichreducethecompressionrate,computation,andsoonwere
proposed,thecompressionstillhavesomethingcanbeimprove.Sincecodingis
developedstrongly,andthecompressionrateforisreducedpowerfullybecause
ofthetimeredundancy.Thus,wetriedtoemploysometechniqueincodingto
improvestillimagecompression.AftertheappearanceofH.264/AVC,theresome
peopleutilizetheintrapredictionapproachofittouseinstillimagecoding,andit
improvethecodingefficiency.
Intrapredictionisaneffectivemethodforreducingthecodedinformationofanimage
oranintraframewithinasequence.Theconventionalmethodtodayistocreate
asamplepredictorblockbyextrapolatingthereconstructedpixelssurroundingthe
targetblocktobecoded.Thesamplepredictorblockissubtractedfromthetargetblock
andtheresultingresidualcodedusingtransformation,quantizationandentropycoding.
Thisisefficientmethodforintraprediction.However,therearetwodrawbacksforthis
method.First,theextrapolationmethodisnotabletorepresentsampleprediction
blockswithcomplextexture.Furthermore,pixelsthatarefarfromthesurrounding
pixelsareusuallybadlypredicted.Inthistutorial,wewillintroduceanewmethodby
templatematchingofreconstructedpixels.
Afterintrapredictionbytemplatematchingisproposed,intrapredictionbyaveraged
templatematchingpredictorsisproposed.Itconsistsofsomeimprovementsand
refinementsofthesamplepredictorblockcreationmethod.Multiplecandidatesample
predictorblockswerecreatedusingtemplatematc