Buffer around a value in a matrix.

Hi I am struggling with building a buffer of values around a specific value in a matrix. For example I have a matrix

A=[ 0 0 0 0 1 0 0 1
    1 0 0 0 0 1 1 1
    0 0 0 0 1 1 1 1
    0 0 0 0 1 1 1 0
    1 0 0 0 1 1 0 0]

The intended matrix with a square buffer filled by 2 around all cells which are 1 (cells which are adjascent and diagonal). Thanks

B=[ 2 2 0 2 1 2 2 1
    1 2 0 2 2 1 1 1
    2 2 0 2 1 1 1 1
    2 2 0 2 1 1 1 2
    1 2 0 2 1 1 2 2]

[Jonas]

i guess it should be

B=[ 2 2 0 2 1 2 2 1
    1 2 0 2 2 1 1 1
    2 2 0 2 1 1 1 1
    2 2 0 2 1 1 1 2
    1 2 0 2 1 1 2 2]

?

[SChow]

Yes, exactly. Sorry for the glitch there.

Corrected now

Answer 1

[Jonas]

A=[ 0 0 0 0 1 0 0 1
    1 0 0 0 0 1 1 1
    0 0 0 0 1 1 1 1
    0 0 0 0 1 1 1 0
    1 0 0 0 1 1 0 0];

B=imfilter(A,ones(3))

B = 5×8

1 1 0 1 2 3 4 3 1 1 0 2 4 6 7 5 1 1 0 2 5 8 8 5 1 1 0 3 6 8 6 3 1 1 0 2 4 5 3 1

B(B>0)=2

B = 5×8

2 2 0 2 2 2 2 2 2 2 0 2 2 2 2 2 2 2 0 2 2 2 2 2 2 2 0 2 2 2 2 2 2 2 0 2 2 2 2 2

B(A==1)=1

B = 5×8

2 2 0 2 1 2 2 1 1 2 0 2 2 1 1 1 2 2 0 2 1 1 1 1 2 2 0 2 1 1 1 2 1 2 0 2 1 1 2 2

isequal(B,[ 2 2 0 2 1 2 2 1
    1 2 0 2 2 1 1 1
    2 2 0 2 1 1 1 1
    2 2 0 2 1 1 1 2
    1 2 0 2 1 1 2 2])

ans = logical
   1