Image segmentation

Hi... I am beginner in image processing. i want to segment the grayscale image Histogram normalization Based Segmentation Mode Delineation. i have given the code blow. please tell me guys how to segment the image mode delineation.

a=imread('14.jpg');

if size(a,3)==3
a1=rgb2gray(a);

end
% figure,imshow(a);
%  contour(a)
[r c d]=size(a);
%  a(a==0)=1;
%  a(a==255)=254;

a=im2double(a1);

   b1=imhist(a);
   figure,plot(b1);
  [x y]=size(b1);
  k=1;
    for i=1:y
        for j=2:x
            n(i,j)=b1(j,i)-b1(j-1,i);
            k=k+1;
        end
    end

    figure,plot(n);

%   [f,x] = imhist(a);
% % %   subplot(2, 2, 1);
%   figure, plot(bins,counts);
%   

% Normalize one way - by the max count height
% y=(x-min(min(x)))/(max(max(x))-min(min(x)));
% figure,plot(y);

normCount1 =abs( n/max(n));%/sum(n);
normCount1=smooth(normCount1);

% % subplot(2, 2, 2);
figure,plot(normCount1);

[B, A] = butter(2, 0.25, 'low');
filtered =filtfilt(B, A,normCount1);
J=a1;
figure,plot(filtered);

thank's in advance...