Contrast Transformation

clc;  %clear cmd window
clear all;  %clear memory

%f=[23 32 21 24;23 255 200 0;1 99 92 45;21 56 73 85]
f=imread('pout.tif'); %read image in an matrix

[row,col]=size(f)  % get size of matrix

r1=50; %till this original image are supposed to be dark
r2=200; %from 51 to 170 it is supoosed to be bright

%value of slopes
alpha=0;
beta=1.5;
gamma=0.3;

% calculating coressponding values of r1 and r2
s1=alpha*r1;
s2=beta*(r2-r1)+r1;


for x=1:1:row
    for y=1:1:col
        
          if 0<=f(x,y) && f(x,y)<=r1
              g(x,y)=alpha*f(x,y);
              
          elseif r1<=f(x,y) && f(x,y)<=r2
              g(x,y)=beta*(f(x,y)-r1)+s1;
              
          else 
              g(x,y)=gamma*(f(x,y)-r2)+s2;
          end
    end
end

%g

figure(1), imshow(f), title('original image')  %display of matrix as img
figure(2), imshow(g), title('Contrasted image')