Merge Two Closely Overlapping Contours

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Hi,

Say I have these two shapes,

They can be represented by contours. I have identified the contour points that are close together. I want to merge them if their edges are close together.

How do I create another contour path that represents the merged shape?

I have tried convex_hull on the concatenation of the two paths, but that only works on convex shapes!

Is there any algorithm that works on concave shapes?