pkg load image

clear
clc

I = imread('peppers.bmp');
I2 = I;
I3 = I;

for i = 1 : 256
  for j = 1 :256
    if (I(i,j)<128)
      I2(i,j) = I(i,j) - 0.3*I(i,j);
    else
      I2(i,j) = I(i,j) + 0.3*I(i,j);
    endif
  endfor
endfor

for i = 1 : 256
  for j = 1 :256
    if (I(i,j)<128)
      I3(i,j) = I(i,j) + 0.3*I(i,j);
    else
      I3(i,j) = I(i,j) - 0.3*I(i,j);
    endif
  endfor
endfor

subplot(2,3,1), imshow(I, [0 255]), title('Original')
subplot(2,3,2), imshow(I2, [0 255]), title('Transformed 1')
subplot(2,3,3), imshow(I3, [0 255]), title('Transformed 2')
subplot(2,3,4), imhist(I)
subplot(2,3,5), imhist(I2), axis([0 256 0 3000])
subplot(2,3,6), imhist(I3), axis([0 256 0 2000])