#! /usr/bin/env python3
#
def delaunay_test ( ):

  from scipy.spatial import Delaunay
  import matplotlib.pyplot as plt
  import numpy as np

  points = np.loadtxt ( 'i18.txt' )
#
#  Display just the points.
#
  plt.clf ( )
  plt.plot ( points[:,0], points[:,1], 'o' )
  for i in range ( 0, 18 ):
    s = str(i)
    plt.text ( points[i,0]+0.15, points[i,1]+0.15, s )
  plt.grid ( 'True' )
  plt.axis ( 'equal' )
  filename = 'i18_points_labeled.png'
  plt.savefig ( filename )
  print ( '  Graphics saved as "' + filename + '"' )
  plt.show ( )
  plt.close ( )
#
#  Display an arbitrary triangulation.
#
  t = np.array ( [ \
    [0,2,1], \
    [0,1,17], \
    [0,17,16], \
    [1,2,3], \
    [1,3,7], \
    [1,7,8], \
    [1,8,15], \
    [3,6,7], \
    [3,4,6], \
    [4,11,6], \
    [5,6,9], \
    [5,9,8], \
    [5,8,7], \
    [5,7,6], \
    [6,11,10], \
    [6,10,9], \
    [8,9,14], \
    [8,14,13], \
    [8,13,15], \
    [9,10,11], \
    [9,11,14], \
    [11,12,14], \
    [12,16,13], \
    [12,13,14], \
    [13,16,15],
    [15,16,17] ] )
  plt.clf ( )
  plt.triplot ( points[:,0], points[:,1], t )
  plt.plot ( points[:,0], points[:,1], 'o' )
  for i in range ( 0, 18 ):
    s = str(i)
    plt.text ( points[i,0]+0.15, points[i,1]+0.15, s )
  plt.grid ( 'True' )
  plt.axis ( 'equal' )
  plt.title ( 'Arbitrary triangulation' )
  filename = 'i18_triangulation_bad.png'
  plt.savefig ( filename )
  print ( '  Graphics saved as "' + filename + '"' )
  plt.show ( )
  plt.close ( )
#
#  Display Delaunay triangulation.
#
  tri = Delaunay ( points )
  plt.clf ( )
  plt.triplot ( points[:,0], points[:,1], tri.simplices )
  plt.plot ( points[:,0], points[:,1], 'o' )
  for i in range ( 0, 18 ):
    s = str(i)
    plt.text ( points[i,0]+0.15, points[i,1]+0.15, s )
  plt.grid ( 'True' )
  plt.axis ( 'equal' )
  plt.title ( 'Delaunay triangulation' )
  filename = 'i18_triangulation_delaunay.png'
  plt.savefig ( filename )
  print ( '  Graphics saved as "' + filename + '"' )
  plt.show ( )
  plt.close ( )

  return

if ( __name__ == "__main__" ):
  delaunay_test ( )