www.pudn.com > threshold.rar > rltentrpthreshold2D.m

function [KL,KJ,KG]=rltentrpthreshold2D(im) 
% RLTENTRPTHRESHOLD2D thresholds gray-scale image using Local Relative Entropy,  
% Joint Relative Entropy and Globle Relative Entropy methods 
% input is image IM 
% output are: 
% KL : local relative entropy threshold 
% KJ : joint relative entropy threshold 
% KG : global relative entropy threshold 
% Programmed By Yingzi (Eliza) Du on 03/08/2004 
 
mn=min(min(im))+1; 
mx=max(max(im))+1; 
his2 = hist2D(im); 
Nm=zeros(1,256); 
k=0; 
 
ml=100000; 
mj=100000; 
mg=-100000; 
his=hist(im); 
for i=mn:mx 
    if his(i)>0 
       k=k+1; 
    end; 
    Nm(i)=k; 
end;   
 
for i=mn:mx-1; 
   Hge=0; 
   Hle=0; 
   Hje=0; 
   Pa=sum(sum(his2(mn:i,mn:i))); 
   Pb=sum(sum(his2(mn:i,i+1:mx))); 
   Pc=sum(sum(his2(i+1:mx,i+1:mx))); 
   Pd=sum(sum(his2(i+1:mx,mn:i))); 
   qa=0; 
   qb=0; 
   qc=0; 
   qd=0; 
   %this part to make sure there is no 0 for the information calculation 
   %calculate the new local, joint and relative entgopy 
   Hr=0; 
   hisa=his2(mn:i,mn:i); 
   hisb=his2(mn:i,i:mx); 
   hisc=his2(i+1:mx,i+1:mx); 
   hisd=his2(i+1:mx,mn:i); 
   area1=Nm(i); 
   area2=Nm(mx)-area1; 
   if (Pa>0) 
      qa=Pa/area1/area1; 
      Hle=-Pa.*log(qa./(Pa+Pc)); 
      hisa=(hisa==0)+hisa; 
      Hle=Hle+sum(sum(hisa.*log(hisa))); 
      Hge=Pa*log(qa); 
   end; 
   if (Pb>0) 
      qb=Pb/area2/area1; 
      Hje=-Pb*log(qb/(Pb+Pd)); 
      hisb=(hisb==0)+hisb; 
      Hje=Hje+sum(sum(hisb.*log(hisb))); 
      Hge=Hge+Pb*log(qb); 
  end; 
   if (Pc>0 ) 
     qc=Pc/area2/area2; 
     Hle=Hle-Pc*log(qc/(Pa+Pc)); 
     hisc=(hisc==0)+hisc; 
     Hle=Hle+sum(sum(hisc.*log(hisc))); 
     Hge=Hge+Pc*log(qc); 
   end; 
   if (Pd>0) 
      qd=Pd/area1/area2; 
      Hje=Hje+Pd*log(qd/(Pb+Pd)); 
      hisd=(hisd==0)+hisd; 
      Hje=Hje+sum(sum(hisd.*log(hisd))); 
      Hge=Hge+Pd*log(qd); 
   end; 
   if Pa+Pc>0 
     Hle=Hle./(Pa+Pc)-log(Pa+Pc); 
     if Hle0) 
      Hje=Hje./(Pb+Pd)-log(Pb+Pd); 
      if(Hjemg 
      mg=Hge; 
      KG=i-1; 
   end; 
end;