Question

I am working on a project in which I am given with a filter K. I need to:

Find a matrix A such that each row of matrix A is the concatenation of
pixels corresponding to the filter K.

K = [ k11 k12 k13 
      k21 k22 k23 
      k31 k32 k33]

I am unable to find A. I am using MATLAB.

Answer 1

As you are talking about pixels, I assume you want to do two dimensinal kernel smoothing.

As K is a 3×3 matrix I suspect that to determine given an input matrix Image you can find a certain point of A in the following way:

for i = 2:size(Image,1)-1
    for j = 2:size(Image,2) -1
        A(i,j) = sum(sum( Image(i-1:i+1,j-1:j+1) .* K ))
    end
end

Of course you will still need to choose how to deal with the edges/corner cases, but I will leave that to you.