function psnr_out = calculate_psnr(f, g)
    df = double(f);
    dg = double(g);
    [m, n] = size(df);
    mse = sum((df - dg).^2, 'all') / (m*n);
    ratio = max(df(:))^2 / mse;
    psnr_out = 10*log10(ratio);
end