Calculate discrete convolution w*f using the minimum zero padding (i.e., add one-element border of 0s all around the image f to form a 7x7 matrix)

and show the final full convolution

image:

[ 0 0 0 0 0

0 0 1 0 0

0 0 1 0 0

0 0 1 0 0

0 0 0 0 0]

kernel:

[ 1 2 1

2 4 2

1 1 1]

rotate kernel first, its convolution