I am trying to implement the constrained least squares filtering as described in Rafael C. Gonzalez, Richard E. Woods - Digital Image Processing 3rd Edition Section 5.9. The equation (
5.9-4) says that $ P \left( u, v \right) $ is the Fourier transformation of the Laplacian filter ($ 3 x 3 $). But the coordinates $u$, $v$ are the coordinates of the image which is much greater than 3x3.
How can I implement this 2D Filter in Frequency Domain?