I have a collection of vertices that have been drawn sequentially by a user and I need to count how many enclosed areas there are within this shape. I have managed to find the intersecting points of crossing segments so I was thinking of walking along the path the initial shape was drawn since I have the direction each edge was drawn but, I'm unsure how to create a collection of polygons found within the shape.

Any help would be greatly appreciated!

Example of a shape I'm dealing with:

CodePudding user response：

Assuming you have list of edges for every vertex:

Choose the lowermost vertex (below 4 at your picture).

Follow the edge with smallest angle from OX.

If vertex has more than one outgoing edges, put it into a queue and follow the last edge in CCW order.

In this case you go around region 4 until initial point is met, putting three vertices in the queue. Then extract vertex (here rightmost) and walk around region 5, next region 3, then 2 and 1.

CodePudding user response：

If you are using NetTopologySuite you can use NetTopologySuite.Operation.Polygonize.Polygonizer. You have to make sure that your input LineStrings are correctly noded.