UGC NET CSE | December 2014 | Part 3 | Question: 64

Question

Given two spatial masks

$S_{1}= \begin{bmatrix}
0&1&0 \\
1&-4&0 \\
0&1&0
\end{bmatrix}$ 

$S_{2} = \begin{bmatrix}
1&1&1 \\
1&-8&1 \\
1&1&1
\end{bmatrix}$

The Laplacian of an image at all points $(x, y)$ can be implemented by convolving the image with spatial mask. Which of the following can be used as the spatial mask ?

• A. only $S_{1}$
• B. only $S_{2}$
• C. Both $S_{1}$ and $S_{2}$ 
• D. None of these 

Answer 1

The ans is S2 only i.e option B

spatial mask  for point (x,y) used to implement the digital  Laplacian of the 2-D is given by

[ f(x+1,y),f(x-1,y),f(x,y+1),f(x,y-1)]-4f(x,y) so possible mask are 

0   1   0              1      1    1

1  -4   1     or      1      8     1  

0   1   0              1      1     1

here in S1  a 1  is missing on the right side of -4