Question

Let us assume we have the following 2d array:

2 1 2 2 1 1 
2 2 1 2 1 1 
2 1 3 2 1 1 
2 2 2 1 3 3 
2 2 1 1 3 3 
2 2 1 1 3 3 

Now, I want to find contiguous regions in the above. Two locations belong to a contiguous region if there is a path between them and their values are the same. Moreover, all nodes in the path should also have the same value. For example, We can divide the above into the following 5 regions:

A B A A D D 
A A B A D D 
A B C A D D 
A A A D E E
A A D D E E 
A A D D E E 

You are allowed to go in all 8 directions. I am looking for an implementation in Java. Can someone please help me with this. The interface is something like

VectorFeature returnComp(int matrix[][])

where VectorFeature can be as follows

class VectorFeature{
  string region
  int numberForRegion
  int numOfElements

}

I Know the idea of how to implement this but i am looking for a fast/ bug free implementation in JAVA!

Answer 1

You could do worse than starting at Wikipedia: Connected-component labeling.