pkg load image
clear
clc

I = imread('cameraman.bmp');
I2 = uint8(zeros(256));
I3 = uint8(zeros(256));
I4 = uint8(zeros(256));

% switch rows
for i = 1 : 2 : 255
  I2(i,:) = I(i+1,:);
  I2(i+1,:) = I(i,:);
endfor

% switch columns
for j = 1 : 2 : 255
  I3(:,j) = I(:,j+1);
  I3(:,j+1) = I(:,j);
endfor
clear i, j;

% switch rows and columns
for i = 1 : 2 : 255
  I5(i,:) = I(i+1,:);
  I5(i+1,:) = I(i,:);
endfor
for j = 1 : 2 : 255
  I4(:,j) = I5(:,j+1);
  I4(:,j+1) = I5(:,j);
endfor


H5x5 = (1/25)*ones(5);
Hw = (1/16)*[1 2 1; 2 4 2; 1 2 1];
I4fa = imfilter(I4, H5x5);
I4fb = imfilter(I4, Hw);
I4fc = ordfilt2(I4, 5, ones(3));

psnr_I_I4fa = psnr(I, I4fa, 255);
psnr_I_I4fb = psnr(I, I4fb, 255);
psnr_I_I4fc = psnr(I, I4fc, 255);

subplot(2,3,1), imshow(I,[0 255]), title('Original')
subplot(2,3,2), imshow(I4,[0 255]), title('Rows and columns switched')

subplot(2,3,4), imshow(I4fa,[0 255]), title('Average filtered')
subplot(2,3,5), imshow(I4fb,[0 255]), title('Weighted average filtered')
subplot(2,3,6), imshow(I4fc,[0 255]), title('Median filtered')