Region Adjacency Graph

## Example Images
![figure_1](https://cloud.githubusercontent.com/assets/3823490/3291718/5ce9b952-f587-11e3-8c29-e2aace6d7794.png)
![figure_2](https://cloud.githubusercontent.com/assets/3823490/3291723/7074b134-f587-11e3-8c73-d28222891a21.png)


![merge](https://cloud.githubusercontent.com/assets/3823490/3372703/28db868c-fbad-11e3-8ed0-465f8d2fed71.jpg)

## Threshold Cut
It will remove edge (A,B). Following which, all regions will still be connected and get the same label

## Hierarchical Merging
Consider Merging (A,C) and call it X. If we keep the weight `15`, (X,B) won't be combined later. However, keeping the weight `5` would ensure that all 3 nodes eventually get merged into one