Seite - 48 - in Document Image Processing

J. Imaging 2018,4, 57 Imean= (∑M−1n=0 In)+ Icen M+1 . (5) Thevalueof f(x) is computedasgiven inEquation(2).As ILBPadditionallyconsiders thecenter pixel, thus thevalueof ILBP(M,R)(xcen,ycen)canvaryfrom1to511 (seeFigure2). Figure2. Illustrationof ILBPvaluegenerationfora3×3gray imagewindow,whereM=8,Radius=1 and Imean=94. Thebit representing thecenterpixelhasbeenunderlined in thebinaryrepresentation of theLBPvalue. 2.2. Rotation InvariantLBP(RILBP) RILBP[22] isachievedbybit-wiserotation(circularly)of thebinarypatternsandthenbyselecting theminimumvalue. This isdonetocancelout theeffectof rotationonatexture,whichchanges the pattern,althoughthe texture inconsideration isessentially thesame.RILBPcanformallybedefined as follows: RILBP(M,R)(xcen,ycen)=min{Rot(LBP(M,R), i|0≤ i≤M−1)}. (6) Here,Rot(A, i) isa functionthat takesanM-bitbinarypattern ‘A’ andperforms i timecircular bit-wiserightshiftoperationon‘A’.Theentireprocess is showninFigure3. Figure3. IllustrationofRILBPvaluegeneration for a3×3gray imagewindow,whereM=8and Radius=1. Thebinarypattern is rotatedclockwisehere. 2.3.UniformLBP(ULBP) InULBP[22], thebinarypatternswith less thanorequal to twonumbersofzero/onetransitions areconsideredasuniformpatternsandtherestareconsideredasnon-uniformpatterns. In thisvariant 48