Bounding box on clusters in a 2D list

[Bengt Richter]

On 23 Apr 2005 13:17:55 -0700, "superprad at gmail.com" <superprad at gmail.com> wrote:

>If I have
>
>ex: x = [[1,1,1,0,0,0,0,0,0,0,0,1,1,1,1,0,0,0],
>         [1,1,1,0,1,1,0,0,0,0,0,1,1,1,1,0,0,0],
>         [1,1,1,0,1,1,1,0,1,1,0,1,1,1,0,0,0,0],
>         [0,0,0,0,0,0,0,0,1,1,0,0,0,0,0,0,0,0]]
>what I want is a boundingbox over the region where we find clusters of
>1's.So for instance in the above list first 3 roes and colums have 1's
>so the area of that box is 3x3
>so my final array should have an array of approx areas of clusters of
>1's like
>area = [ 9,4 ....]
Where does the 4 come from?

>Hope I am clear with my question.
>
Not quite clear on if "clusters" have to be rectangular and fill their bounding boxes
or whether

    [[0, 0, 0, 0, 0],
        +-----+
     [0,|1, 1,|0, 0],
        |     |
     [0,|0, 1,|0, 0],
        +-----+
     [0, 0, 0, 0, 0]]

is a cluster with three 1's. Or indeed whether "bounding boxes" have to be rectangular.
I.e., what about diagonal clusters?
           ,__,
    [[0, 0,|1,|0, 0],
         _/ _/   ,__, 
     [0,/1,/0, 0,|1],
      _/ _/    _/ /
     [1,/0, 0,/1,/0],
            _/ /
     [0, 0,/1,/0, 0]]

Or should that be
      +-------------+
    [[|0, 0, 1, 0, 0|],
      |             |
     [|0, 1, 0, 0, 1|],
      |             |
     [|1, 0, 0, 1, 0|],
      |             |
     [|0, 0, 1, 0, 0|]]
      +-------------+

since two 3x3 squares around the length-3 diagonals would overlap.

Regards,
Bengt Richter