xray=imread('x-ray_angiogram.jpg');
xray=rgb2gray(xray);
[M,N] = size(xray);
%find original rmin
    MAX=xray(1,1);
    for i=1:M
        for j=1:N
            if MAX <= xray(i,j);
                MAX=xray(i,j);
            end
         end
    end
%find original rmax
    MIN=xray(1,1);
    for i=1:M
        for j=1:N
            if MIN >= xray(i,j);
             MIN=xray(i,j);
            end
        end
    end

%apply contrast stretching
slope = 255/(MAX-MIN);
intercept = 255 - slope*MAX;
xraystretched = slope.*xray + intercept;