clear all;
lena = imread('lena.tiff');
lena_gray = rgb2gray(lena);
lena_gray_downsampled = imresize(lena_gray, 0.25, 'bilinear');
lena_gray_upsampled_nearest = imresize(lena_gray_downsampled, 4, 'nearest');
lena_gray_upsampled_bilinear = imresize(lena_gray_downsampled, 4, 'bilinear');
lena_gray_upsampled_bicubic = imresize(lena_gray_downsampled, 4, 'bicubic');

cameraman = imread('cameraman.tiff');

imshow(lena)
title('Lena')
figure

imshow(lena_gray)
title('Lena Gray')
figure

imshow(lena_gray_downsampled)
title('Lena Gray Downsampled 4x Bilinear')
figure

imshow(lena_gray_upsampled_nearest)
title('Lena Gray Upsampled 4x Nearest')
lena_gray_psnr_nearest = calculate_psnr(lena_gray, lena_gray_upsampled_nearest)
figure

imshow(lena_gray_upsampled_bilinear)
title('Lena Gray Upsampled 4x Bilinear')
lena_gray_psnr_bilinear = calculate_psnr(lena_gray, lena_gray_upsampled_bilinear)
figure

imshow(lena_gray_upsampled_bicubic)
title('Lena Gray Upsampled 4x Bicubic')

lena_gray_psnr_bicubic = calculate_psnr(lena_gray, lena_gray_upsampled_bicubic)