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

4 4 4 4 4 4 4 4 4 4
4 3 3 3 3 3 3 3 3 4
4 3 2 2 2 2 2 2 3 4
4 3 2 1 1 1 1 2 3 4
4 3 2 1 1 1 1 2 3 4
4 3 2 1 1 1 1 2 3 4
4 3 2 1 1 1 1 2 3 4
4 3 2 2 2 2 2 2 3 4
4 3 3 3 3 3 3 3 3 4
4 4 4 4 4 4 4 4 4 4

for (int gen = 1; gen <= 4; gen++)
{
    for (int x = 1; x < arrayWidth - 1; x++)
    {
        for (int y = 1; y < arrayHeight - 1; y++)
        {
            // See if this cell is in the current generation.
            if (_generation[x + arrayWidth * y] == gen)
            {
                // Generate next generation.
                for (int i = x - 1; i <= x + 1; i++)
                {
                    for (int j = y - 1; j <= y + 1; j++)
                    {
                        if (_generation[i + arrayWidth * j] == 0 || _generation[i + arrayWidth * j] > gen)
                        {
                            _generation[i + arrayWidth * j] = gen + 1;
                        }
                    }
                }
            }
        }
    }
}

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

0 0 0 3 3 3 3 3 3 3 3 0 0 0
0 0 3 3 2 2 2 2 2 2 3 3 0 0
0 3 3 2 2 1 1 1 1 2 2 3 3 0
3 3 2 2 1 1 1 1 1 1 2 2 3 3
3 2 2 1 1 1 1 1 1 1 1 2 2 3
3 2 1 1 1 1 1 1 1 1 1 1 2 3
3 2 1 1 1 1 1 1 1 1 1 1 2 3
3 2 1 1 1 1 1 1 1 1 1 1 2 3
3 2 1 1 1 1 1 1 1 1 1 1 2 3
3 2 1 1 1 1 1 1 1 1 1 1 2 3
3 2 2 1 1 1 1 1 1 1 1 2 2 3
3 3 2 2 1 1 1 1 1 1 2 2 3 3
0 3 3 2 2 1 1 1 1 2 2 3 3 0
0 0 3 3 2 2 2 2 2 2 3 3 0 0
0 0 0 3 3 3 3 3 3 3 3 0 0 0

1 0 0 0 0 0 0 1
0 1 0 0 0 0 1 0
0 0 1 0 0 1 0 0
0 0 0 1 1 0 0 0

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

0 0 0 0 0 3 3 3 3 0 0 0 0 0
0 0 0 0 3 2 2 2 2 2 3 0 0 0
0 0 0 3 2 1 1 1 1 2 3 0 0 0
0 0 3 2 1 1 1 1 1 1 2 3 0 0
0 3 2 1 1 1 1 1 1 1 1 2 3 0
3 2 1 1 1 1 1 1 1 1 1 1 2 3
3 2 1 1 1 1 1 1 1 1 1 1 2 3
3 2 1 1 1 1 1 1 1 1 1 1 2 3
3 2 1 1 1 1 1 1 1 1 1 1 2 3
3 2 1 1 1 1 1 1 1 1 1 1 2 3
0 3 2 1 1 1 1 1 1 1 1 2 3 0
0 0 3 2 1 1 1 1 1 1 2 3 0 0
0 0 0 3 2 1 1 1 1 2 3 0 0 0
0 0 0 3 2 2 2 2 2 2 3 0 0 0
0 0 0 0 3 3 3 3 3 3 0 0 0 0

im = imcircle(70);
im = padarray(im,[20,20]);
figure;imshow(im);
im2 = imdilate(im,strel('disk',8));
figure;imshow(im2);