Descartes
=========

Use Shapely_ or GeoJSON-like geometric objects as matplotlib paths and patches

.. image:: http://farm4.static.flickr.com/3662/4555372019_9bbed1f956_o_d.png
   :width: 800
   :height: 320

Requires: matplotlib, numpy, and optionally Shapely 1.2+.

Example::

  from matplotlib import pyplot
  from shapely.geometry import LineString
  from descartes import PolygonPatch
  
  BLUE = '#6699cc'
  GRAY = '#999999'
  
  def plot_line(ax, ob):
      x, y = ob.xy
      ax.plot(x, y, color=GRAY, linewidth=3, solid_capstyle='round', zorder=1)
  
  line = LineString([(0, 0), (1, 1), (0, 2), (2, 2), (3, 1), (1, 0)])
  
  fig = pyplot.figure(1, figsize=(10, 4), dpi=180)
  
  # 1
  ax = fig.add_subplot(121)
  
  plot_line(ax, line)
  
  dilated = line.buffer(0.5)
  patch1 = PolygonPatch(dilated, fc=BLUE, ec=BLUE, alpha=0.5, zorder=2)
  ax.add_patch(patch1)
  
  #2
  ax = fig.add_subplot(122)
  
  patch2a = PolygonPatch(dilated, fc=GRAY, ec=GRAY, alpha=0.5, zorder=1)
  ax.add_patch(patch2a)
  
  eroded = dilated.buffer(-0.3)
  
  # GeoJSON-like data works as well
  
  polygon = eroded.__geo_interface__
  # >>> geo['type']
  # 'Polygon'
  # >>> geo['coordinates'][0][:2]
  # ((0.50502525316941682, 0.78786796564403572), (0.5247963548222736, 0.8096820147509064))
  patch2b = PolygonPatch(polygon, fc=BLUE, ec=BLUE, alpha=0.5, zorder=2)
  ax.add_patch(patch2b)
  
  pyplot.show()


See also: examples/patches.py.

Descartes is not associated with the identically named and apparently defunct
project at http://descartes.sourceforge.net/.

.. _Shapely: http://gispython.org/lab/wiki/Shapely