pkg load image

clear
clc

I = imread('cameraman.bmp');

I2 = uint8(zeros(260));
I2(1:256,1:256) = I;
I3 = uint8(zeros(260));
I3(1:256, 5:260) = I;
I4 = uint8(zeros(260));
I4(5:260, 1:256) = I;
I5 = uint8(zeros(260));
I5(5:260, 5:260) = I;

Ir = 0.25*I2 + 0.25*I3 + 0.25*I4 + 0.25*I5;
IrCropped = Ir(3:258, 3:258);

H = (1/25)*ones(5);

IavgFILT = imfilter(IrCropped, H);
ImedFILT = ordfilt2(IrCropped, 13, ones(5));

pnsrAVG = psnr(IavgFILT, I, 255);
pnsrMED = psnr(ImedFILT, I, 255);

subplot(2,3,1), imshow(I, [0 255]), title('Original')
subplot(2,3,2), imshow(Ir, [0 255]), title('Shifted slightly')
subplot(2,3,3), imshow(IrCropped, [0 255]), title('Cropped to 256x256')
subplot(2,3,4), imshow(IavgFILT, [0 255]), title('3x3 AVG filtered')
subplot(2,3,5), imshow(ImedFILT, [0 255]), title('3x3 MEDIAN filtered')