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)


Di we really increase dimensionality here? Depth does not occur above.

Also, I much prefer (M, N, ...) rather than (width, height). (Especially, since it is typically the other way round)