%% OTSU automatic thresholding method
sumB = 0;
wB = 0;
maximum = 0;
threshold1 = 0.0;
threshold2 = 0.0;
sum1 = sum((1:levels).*histogramCounts.'); % the above code is replace with this single line
subplot(1,4,1);imshow(im,[0 levels]);

for ii=1:levels
    wB = wB + histogramCounts(ii);
    if (wB == 0)
        continue;
    end
    wF = total - wB;
    if (wF == 0)
        break;
    end

%---debug ---
Bx=histogramCounts(1:ii);Fx=histogramCounts(ii+1:levels);
weightB=sum(Bx)/sum(histogramCounts);
weightF=sum(Fx)/sum(histogramCounts);
meanB=(sum(Bx.*[0:ii-1]'))/sum(Bx);
meanF=sum(Fx.*[ii:levels-1]')/sum(Fx);
Between=weightB*weightF*((meanB-meanF)^2);

   if ( Between > maximum )
        threshold1 = ii;
        maximum = Between;
    end
message(ii,:)=[ii meanB weightB meanF weightF Between];
level =threshold1;% (threshold1 + threshold2 )/(2);
disp([num2str(ii) ' : '  num2str(Between)]);
subplot(1,4,1);imshow(im,[0 levels]);
subplot(1,4,2);bar(histogramCounts);hold on;plot(ii,max(histogramCounts)/2,'x','color','r');plot(level,max(histogramCounts)*(2/3),'x','color','g');hold off;
set(gca,'XTickLabel',{0:levels-1});
subplot(1,4,3);imshow((im>ii));
subplot(1,4,4);imshow((im>level));
drawnow();
  
%pause();

end