In a Javascript-based environment, I am starting with points that define segments of a Hilbert curve, e.g., an order-7 curve, partitioned into 24 arbitrary segments defined over a 128 x 128 2D space:

For each segment, given sets of points (x, y) for that segment, I would like to find the edges of the concave polygon that bounds those points.

For example, for segment 1, I would like to define a set of points that outline its associated concave polygon, as shown in this sketch(*):

And so on, for segments 2 through 24.

What are common algorithms for finding the edges of concave polygons defined by a set of points, some/most of which may be inside said polygon?

Javascript implementations are great. Pseudocode is fine, as well, which can be reimplemented in Javascript.

(*: By sketch, I mean just that. This is not an "implementation" but a sketch made in an illustration tool. Thanks for answering the question, as written!)