sample neighboring elements in a matrix

 r  = round(0.5+randi(8,size(10,10))*8); % I have the matrix of random integers
 r1 = r(1:3:end,1:3:end); % I sample every element separated by 3 elements in 2D.

I now want to treat each random number as indicating a neighboring element as:

 1 2 3
 4 r 5
 6 7 8

and return the corresponding neighboring element values in a new variable like:

 r_neigh=r(code to find neighboring values);

but only for the elements in r1.

so if r=

 6  7       5*  4*  1  3
 4  1  6  8  7  4
 2  4  6  3  8  1
 3  2  2  4  6  5
 3  3  5  1  4  5
 2  7  1  5  7  7

Then element r(1,4)=4, would result in r_neigh(1,4)=5 (see asterisks^)

I suspect I can use a conv2 function or something, but I am not sure how because there are 8 possible neighbors. Thank you.

Edit: Also, I know that there will be problems with the boundaries of the matrix, I will cross that bridge when I come to it.