C/C++ :: Two Dimensional Array Median Filtering?

I'm trying to write code that implements [median filtering] on a two-dimensional array.

Here's an image to illustrate:

The program starts at the beginning of the array. The maximum array size is 100. I know that I can use an array like:

int a[100][100];

to store the input, and that I can iterate over a part of this array using two `for` loops like this:

for(i=0;i<size_filter;i++)
for(j=0;j<size_filter;j++)
temp[i][j]=a[i][j] // not so sure

But how can I make this code loop over the neighbors of every element in the array, calculate their median, and replace the center element with the median?

For some examples of what I'm trying to do, let's say that the input is a 5x5 matrix, so the input size is 5. And I want to run a 3x3 median filter on it, i.e. each element should be replaced by the median of the 3x3 elements surrounding it.

The program starts at the corner index (0,0). For this index, it scans the 3x3 region surrounding it (of which only four indexes actually lie within the input array), which contains the values 0, 0, 1, and 0. The median of these values is 0, so that's what the code should output for this array index.

In the picture below, the number in -band - is the center cell, and the plain * and * numbers are its neighbors within the 3x3 region surrounding it:

-0- *0* 0 0 0
*1* *0* 0 1 0
1 1 0 0 0
0 1 1 0 0
0 0 0 0 0

Here's another example, this time with the center index (0,1):

*0* -0- *0* 0 0
*1* *0* *0* 1 0
1 1 0 0 0
0 1 1 0 0
0 0 0 0 0

This time, the elements in the 3x3 region (excluding those outside the input array) have the values 0, 0, 0, 1, 0, and 0, and again, their median is therefore 0.

Here's yet another example, this time from the middle of the input, at center index (3,2):

0 0 0 0 0
*1* *0* *0* 1 0
*1* -1- *0* 0 0
*0* *1* *1* 0 0
0 0 0 0 0

This time, the elements within the 3x3 region have the values 1, 0, 0, 1, 1, 0, 0, 1, and 1, and their median in therefore 1.

Final example:

<size of array><size filter> <data>
8
3
0 0 0 0 0 0 0 0
0 5 0 0 6 0 0 0
0 0 0 0 0 7 0 0
0 0 0 0 5 0 0 0
0 0 0 5 6 0 0 0
0 0 8 5 5 0 0 0
0 0 0 7 0 0 9 0
0 0 0 0 0 0 0 0

Output:

0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0
0 0 0 5 5 0 0 0
0 0 0 5 5 0 0 0
0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0