Plated_hist.m

%% Document Title
% This code removes the unevenness of a histogram to a great extent. 
% Every local minima-maxima pair is replaced by a plate whose height is 
% equal to the average height of the local minima-maxima pair and width
% is equal to the width of the local minima-maxima pair.Thus the histogram   
% is plated and we get a smoother version of the original histogram at 
% the cost of little approximation.
clear all;
i= imread('face6.jpg');
 I= rgb2gray(i);
 imhist(I);
 a= imhist(I);
 plot(a)
 i=1;
 k=1;
 count=1;
 x=0;
 z=0;           
 if a(i)>=a(i+1),   %if there is an increasing slope at the begining of the 
while a(i)>=a(i+1), %histogram we move to the peak.It's the 1st local maxima
z=z+a(i);           %The elements encountered so far are replaced by the 
i=i+1;              %average value.%  
end
z=z+a(i);
while k<=i,
a(k)=floor(z/(i+1));
k=k+1;
end
end
 while i<256                  %This while loop eterates till the last element 
start=i;                      %of the histogram.start holds the starting position of a plate%
while i+1<=256 & a(i)<=a(i+1),%This loop ends when a local crest is reached
x=x+a(i);                     %All the element on the way 2 a local crest is being added up
i=i+1;
end 
while i+1<=256 & a(i)>=a(i+1),  %This loop ends when the end of the 
x=x+a(i);                       %increasing slope,i.e., a local peak 
i=i+1;                          %is reached.
end
x=x+a(i);       %The peak value is added as it doesnt get added inside the loop
if start==0,    %The if block eterates only when there is an decreasing slope
count=i+1;      %at the begining of the histogram
else
count=i-start+1;   %In both the if & else block count conatins the no. of elements visited, by which the sum shud b divided to get the average value 
i=start;           %The begining point of a local minima-maxima pair is assigned to i   
end                %a plate is getting placed instead of the local-minima-maxima.
while i<=start+count-1,
a(i)=floor(x/count);  %Every element of the local minima-maxima pair is   
i=i+1;                %getting replaced by the average value[floor(x/count)],
end                   %eteration ends as we reach the last element of the local minima-maxima pair, 
x=0;                  %x is resetted.It holds the sum of a local minima-maxima pair.
end                   %control goes to line no.20, and another minima-maxima pair is encountered and plated
plot(a)