Note that your MSE may vary slightly depending on how you handle border cases in bilinear transform.
Input image:
Subsampled image.
Restored image using bilinear interpolation.
Difference image. MSE is 582.132.
Subsampled image.
Restored image using bilinear interpolation.
Difference image. MSE is 515.898.
Subsampled image.
Restored image using bilinear interpolation.
Difference image. MSE is 1872.21.
Subsampled image.
Restored image using bilinear interpolation.
Difference image. MSE is 1375.17.