Question

Sounds to me I’ve a very basic need: extracting coordinates of the zones composing a matrix.

Let me give an example. Here is some matrix:

    | A | B | D | E | F | G | H | I | J |
| 1 | 0 | 0 | 0 | 2 | 2 | 2 | 4 | 4 | 4 |
| 2 | 0 | 0 | 2 | 2 | 2 | 2 | 4 | 4 | 4 |
| 3 | 0 | 0 | 2 | 2 | 2 | 3 | 3 | 4 | 4 |
| 4 | 1 | 1 | 1 | 2 | 2 | 3 | 3 | 4 | 4 |
| 5 | 1 | 1 | 1 | 2 | 2 | 3 | 3 | 4 | 4 |
| 6 | 1 | 1 | 1 | 2 | 2 | 3 | 3 | 4 | 4 |
| 7 | 1 | 0 | 0 | 0 | 1 | 1 | 3 | 0 | 4 |
| 8 | 0 | 0 | 0 | 0 | 1 | 1 | 1 | 0 | 0 |
| 9 | 0 | 0 | 0 | 1 | 1 | 1 | 1 | 0 | 0 |
| 10| 0 | 0 | 0 | 1 | 1 | 1 | 1 | 0 | 0 |

And I’d like to get an array with the boundaries and value of each zone (no particular order needed).

Example for the top-left zone:

• value: 0
• boundaries: {A1, D1, B2, B3, 13}

Do you know some library answering this need or should I code this myself?

Answer 1

I’d code this myself, not sure if there are libraries.

I’d consider each point in turn, for each region. Then (i think) this should work:

if (surrounding 8 squares has at least one with different region)
{
    for each 3 squares, above, below, left and right
    {
        if (less than 3 are different, and the middle is different)
        {
            is a boundry
        }
    }

    for each 3 squares, above, below
    {
        for each 3 squares, left, right
        {
            if(all 3 from outer loop and all 3 from inner loop are different)
            {
                is a boundry
            }
        }
    }

    not a boundry
}
else
{
    not a boundry
}

Treat out of bounds squares as different.