title: How to get all points constituting convex hull,if convex hull is perfect rectangle(python 3)?
body: <p><strong>open image to see result of below code</strong> </p>
  
  <pre><code>import numpy as np
  from scipy.spatial import ConvexHull
  import matplotlib.pyplot as plt
  
  points = np.array([[1,1],[1,2],[1,3],[1,4],[2,1],[2,2],[2,3],[2,4],[3,1],[3,2],[3,3],[3,4],[4,1],[4,2],[4,3],[4,4]])  
  hull = ConvexHull(points)
  plt.plot(points[:,0], points[:,1], 'o')
  for simplex in hull.simplices:
      plt.plot(points[simplex, 0], points[simplex, 1], 'k-')
      plt.plot(points[simplex,0], points[simplex,1], 'ro', alpha=.25, markersize=20)
  </code></pre>
  
  <p>I want to get index of coordinate of point that are on convex hull(the points that are black + on line).I choose rectangle just to get an extreme case. </p>
  
  <p><strong><em>hull.points</em></strong> can only give points that are marked red(only corner point of rectangle).</p>
  
  <p><a href="https://i.stack.imgur.com/UD4yV.jpg" rel="nofollow noreferrer">result of code</a></p>