title: algorithm like convex hull, but that return the lower area polygon containing all points
body: <p>I have a spatial software, In a database I have for each street in several cities, the lat/long of each street. And every street belongs to a zone. I'm trying to get polygons for each zone, and to do this, I need an algorithm that give me as result the smallest polygon that covers a number of points. Very similar to convex hull. convex hull is useless because it resolved it like this: </p>
  
  <p><img src="https://i.stack.imgur.com/a4YJb.jpg" alt="enter image description here"></p>
  
  <p>And, what I need is this:</p>
  
  <p><img src="https://i.stack.imgur.com/stFNd.jpg" alt="enter image description here"></p>