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1、MedicalImageProcessingandAnalysisDr.TanyaIvanovskatetyana.ivanovska@uni-greifswald.deInstituteofCommunityMedicineErnst-Moritz-ArndtUniversity,Greifswald,Germany16November2011Lecture4MedicalImageProcessingIntensitytransformationsIntensitytransformationsoperateonsinglepixelsofanimagecontra
2、stmanipulationimagethresholdingEnhancementistheprocessofmanipulatinganimagesothattheresultismoresuitablethantheoriginalforaspecificapplication.Notations=T(r),randsistheimagebeforeandaftertheprocessing,Tisatransformation.02.11.2011Lecture41/14MedicalImageProcessingIntensitytransformationsI
3、mageNegativesAnimagerwithintensitylevelsintherange[0,L−1]Negativetransformationissuitedforvisualenhancingwhiteorgraydetailembeddedindarkregionsdominantinsize.Imagecontentstaysthesame!s=L−1−r(1)02.11.2011Lecture42/14MedicalImageProcessingIntensitytransformationsMatlabcode12I=imread(’test.
4、tif’);3imshow(I)4J=imcomplement(I);5figure,imshow(J)02.11.2011Lecture43/14MedicalImageProcessingIntensitytransformationsLogTransformations=clog(1+r)Compressesthedynamicrangeofimageswithlargevariationsinpixelvalues.Anarrowrangeoflowintensityvaluesismappedintoawiderrange.Thehigherintensityv
5、aluesaremappedintoanarrowerrange.02.11.2011Lecture44/14MedicalImageProcessingIntensitytransformationsLogTransformationinitc=1c=2c=502.11.2011Lecture45/14MedicalImageProcessingIntensitytransformationsMatlabcode1I=imread(’test.tif’);2imshow(I)3I2=im2double(I);4J=1∗log(1+I2);5J2=2∗log(1+I2)
6、;6J3=5∗log(1+I2);7figure,imshow(J)8figure,imshow(J2)9figure,imshow(J3)02.11.2011Lecture46/14MedicalImageProcessingIntensitytransformationsPowerLaw(Gamma)Transformations=crγ,wherecandγarepositiveconstants.similartologtransformation,butusespower-lawcurvesisalsousedforcontrastmanipulation02.11
7、.2011Lecture47/14MedicalImageProcessingIntensitytransformationsGammaTransformationinitγ=3γ=1γ=0.602.11.2011Lecture48/14MedicalImageProcessingIntensitytransformationsMatlabcode1I=imread(’spinetest.pnm’);23J=imadjust(I,[],[],1);4J2=imadjust(I,[],[],3);5J3=imadjust(I,[],[],0
