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+//Ex10_20
+// Variable Thresholding Via Image Partitioning
+// Version : Scilab 5.4.1
+// Operating System : Window-xp, Window-7
+//Toolbox: Image Processing Design 8.3.1-1
+//Toolbox: SIVP 0.5.3.1-2
+//Reference book name : Digital Image Processing
+//book author: Rafael C. Gonzalez and Richard E. Woods
+
+clc;
+close;
+clear;
+xdel(winsid())//to close all currently open figure(s).
+
+
+function th1=otsu(count,cell)
+normal_hist=count/(M/2*N/3);
+Sum=0;
+cumu_mean=0;
+for k=1:max(cell)+1
+    Sum=Sum+normal_hist(k);
+    P1(k)=Sum;
+    cumu_mean=cumu_mean+(k*normal_hist(k));
+    m(k)=cumu_mean;
+    Mg=cumu_mean;
+    sigma_B(k)=(((Mg*P1(k))-m(k))^2)/(%eps+(P1(k)*(1-P1(k))));
+end
+
+th1=find(sigma_B==max(sigma_B));
+endfunction
+
+
+a=imread("Ex10_20.tif");
+a=imresize(a,[650 813],'bicubic');
+a1=im2double(a);
+figure,ShowImage(a,'Gray Image');
+title('Original Image','color','blue','fontsize',4);
+[M,N]=size(a);
+
+[count cell]=imhist(a);
+figure,plot2d3(cell,count);
+title('Histogram','color','blue','fontsize',4);
+
+/////////////////////////////// Iterative Thresholding ///////////////////
+thr = iterthresh(a1);
+b1=im2bw(a1,thr);
+figure,ShowImage(b1,'Gray Image');
+title('Segmentation Using Iterative Global Thresholding','color','blue','fontsize',4);
+
+//////////////////////////////// Otsu Method /////////////////////////////
+
+normal_hist=count/(M*N);
+Sum=0;
+cumu_mean=0;
+for k=1:max(cell)+1
+    Sum=Sum+normal_hist(k);
+    P1(k)=Sum;
+    cumu_mean=cumu_mean+(k*normal_hist(k));
+    m(k)=cumu_mean;
+    Mg=cumu_mean;
+    sigma_B(k)=(((Mg*P1(k))-m(k))^2)/(%eps+(P1(k)*(1-P1(k))));
+end
+
+th=find(sigma_B==max(sigma_B));
+b2=im2bw(a1,(th/255));
+figure,ShowImage(mat2gray(b2),'Binary Image');
+title('Image Segmented using Otsu Threshold','color','blue','fontsize',4); 
+
+/////////////////////////// Otsu with Image Partitioning /////////////////////////////
+count=[];
+cell=[];
+z=1;
+th2=[40 50 70 40 50 70];
+for i=1:M/2:M
+    for j=1:N/3:N
+        [count cell]=imhist(a(i:(i-1)+(M/2),j:(j-1)+(N/3)));        
+        th1=otsu(count,cell);        
+        b3(i:(i-1)+(M/2),j:(j-1)+(N/3))=im2bw(a1(i:(i-1)+(M/2),j:(j-1)+(N/3)),(th2(z)/255));
+        z=z+1;
+    end
+end
+
+figure,ShowImage(mat2gray(b3),'Binary Image');
+title('Image Segmented using Otsu Threshold','color','blue','fontsize',4);