histogram equalization via matlab from scratch

im2imhisteq.m

function new_im = im2imhisteq(I)
    % takes an Input Image and
    %http://www.osmanoglu.org/supplement/unpublishedWork/DigitalImageProcessing_HistogramEqualizationMatching.pdf
    %Manhas, Pratima & Thakral, Shaveta. (2018)...
    %   Comparative analysis of different wavelet ... 
    %   filters and Image enhancement using Histogram Equalization. 
    
    L=256;
    [m,n]=size(I);
    len=m*n; %number of pixels
    dum_hist=imhist(I); % pdf, 1 x L
    probsAll=dum_hist/len; 
    cdfsAll=probsAll'*triu(ones(L));
    new_im=zeros(m,n);
    for k=0:L-1
         if (probsAll(k+1) > 0)
             list=find(I == k);
             new_im(list)=(cdfsAll(k+1)*L); %map sk value for each k valued
         end
    end
   new_im = uint8(new_im); 

end

myhisteq.m

function new_hist = myhisteq(dum_hist)
L = length(dum_hist);
new_hist = zeros(1,L);

total_pixels = sum(dum_hist);
probsAll  = dum_hist/total_pixels;

% calculate CDF
cdfsAll = zeros(1,L);
cdfsAll(1)=probsAll(1);
for i=2:L
    cdfsAll(i) = cdfsAll(i-1)+probsAll(i);
end
% our final result

sk = (cdfsAll * (L-1));
rfval = uint8(sk);

%map to new histogram
for i=1:L
    new_hist(rfval(i)+1) = new_hist(rfval(i)+1)+dum_hist(i);
end

myhistogram.m

function myhist = myhistogram(I)
L=256;
myhist=zeros(1,L);
[m,n]=size(I);
len = m*n;
I1D = reshape(I,len,1);
for i = 1:len
    myhist(I1D(i)+1) = myhist(I1D(i)+1)+1;
end