histogramme_equalization.m

function res= histogramme_equalization(a)
r=size(a,1);
c=size(a,2);
ah=uint8(zeros(r,c));
n=r*c;
f=zeros(256,1);
pdf=zeros(256,1);
cdf=zeros(256,1);
cum=zeros(256,1);
out=zeros(256,1);
    for i=1:r
        for j=1:c
            value=a(i,j);
            f(value+1)=f(value+1)+1;
            pdf(value+1)=f(value+1)/n;
        end
    end
 sum=0; L=255;
    for i=1:size(pdf)
        sum=sum+f(i);
        cum(i)=sum;
        cdf(i)=cum(i)/n;
        out(i)=round(cdf(i)*L);
    end
    for i=1:r
        for j=1:c
        ah(i,j)=out(a(i,j)+1);
        end
    end
    %imshow(ah);
    res=ah;
end