strip polygonize, help please!

Hi every one. I am try to make definition for creation of border, and i have a problem. On the picture below you can see how is looks my problem. I am try two variant. The first one is finding nearest point, but it doesn't work becouse not always nearest point is right point. The second one is using Delaunay algoritm for construct poligon for all point in one strip, and delite outer and inner poligon that don't use in the strip. It doesn't work because Delaunay didn't knows anything about contour of strip. 

So my question is if there way or component to solve this problem?

Defenition pl%20triang%20of%20molding.gh

Picture