Histogram Stretching

Aim:- Histogram Stretching
MSc Computer Science Image Processing Practical No. 14
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Code:- Hist_Stretch.m

% **** HISTOGRAM STRETCHING ****

a=imread('old imagelc.jpg');
aa=double(a);
[row col]=size(aa);
h=zeros(1,300);
rmax=(max(max(aa)));
rmin=(min(min(aa)));
slope=255/(rmax-rmin);
smin=0;
aa=aa+1;
for x=1:row
    for y=1:col
        c(x,y)=slope*(aa(x,y)-rmin)+smin;
    end
end
for x=1:row
    for y=1:col
   %if aa(x,y)==0
    %   aa(x,y)=1;
        t=aa(x,y);
        h(t)=h(t)+1;
    end
end
figure(1);
bar(h);
z=zeros(1,300);
for x=1:row
    for y=1:col
        %if aa(x,y)==0
         %   aa(x,y)=1;
        p=round(c(x,y));
        z(p)=z(p)+1;
    end
end
end
figure(2);
bar(z);
figure(3);
imshow(uint8(c));
figure(4);
imshow(uint8(aa));

Output:-