title: How can I modify the margins when I plot map with cartopy?
body: <p>I use cartopy(following code) to draw world maps. I have set as <code>ax = fig.add_axes([0, 0, 1, 1])</code>. However, the output maps always show large margins over the frames. I want to show the map as full screen or full-size of images.<br>
  How to set the margins of the cartopy plotting?  </p>
  
  <pre><code>import cartopy.crs as ccrs
  import cartopy.feature as cfeature
  import matplotlib.pyplot as plt
  
  fig = plt.figure()
  ax = fig.add_axes([0, 0, 1, 1])
  ax = plt.axes(projection=ccrs.PlateCarree())
  
  ax.add_feature(cfeature.LAND)
  ax.add_feature(cfeature.OCEAN)
  ax.add_feature(cfeature.COASTLINE)
  ax.add_feature(cfeature.BORDERS)
  ax.outline_patch.set_visible(False)
  
  plt.show()
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/RyGvc.png" alt="output img here"></p>