how laplacien it calculated?

hi guys,, i have question about filter laplacien,,

[0 -1 0   *        [28 31 30 =       [ 0  2  3

-1 4 -1            30 32 27  =       4  13  0

0 -1 0 ]          29 27 30 ]        7   0   1 ]..

so I know that 13 is sum of multiplication ..but how value is calculated other(0 2 3,4,7,0,1,0)??

Answer 1

[Image Analyst]

I have no idea. It's not a Laplacian as if you convolve a kernel with an image. It's not a convolution, correlation, or normalized cross correlation. I don't know what it is. Where did you get it, and why do you think it might be correct?