title: Sankey diagram matplotlib save scale issue
body: <p>Using <code>matplotlib</code> to generate a Sankey diagram of data from wikipedia (looks like really bad data but figured I'd figure out the code and then go looking for better data). And I can't seem to get the file to scale correctly.</p>
  
  <p>It <em>displays</em> fine with <code>plt.show()</code> in the system <code>Python.app</code> in macOS 10.12.4, and the simple examples saved <em>fine</em>, but adding <code>scale = 0.0001</code> seems to have destroyed the <code>plt.savefig()</code> somehow. I’ve tried changing the <code>dpi</code> parameter but it doesn't seem to affect the result at all. I also tried adding a <code>scale</code> parameter to <code>savefig</code> but that didn‘t seem to do anything at all (not even break it?).</p>
  
  <p>I can save it from <code>Python.app</code> and it looks fine, but I really wanted to figure out what is going wrong.</p>
  
  <pre><code>import matplotlib.pyplot as plt
  from matplotlib.sankey import Sankey
  
  fig = plt.figure(figsize = (13, 7), frameon = False)
  ax = fig.add_subplot(1, 1, 1, xticks = [], yticks = [], title='Global Electricity Production &amp; Consumption 2005'
                       )
  g = [-12192, 6157, 1960, 387, 2383, 1240]              # generated
  c = [4250, -7942, -1418, -1266, -1017, -8.79]          # consumed
  sankey = Sankey(ax = ax, 
          format = '%.5G', 
          head_angle = 135,  
          unit = ' TWh', 
          gap = 0.3, 
          scale = 0.0001,
          margin = 0.0,
          offset = 0.2,
          shoulder = 0.0)
  
  sankey.add(
      patchlabel = 'Production',
      flows = g,
      orientations = [0, 0, -1, -1, 1, 1], 
      labels = [None, 'Coal', 'Natural Gas', 'Petroleum', 'Nuclear', 'Renewable'],
      pathlengths = [0.0, 0.2, 0.2, 0.6, 0.2, 0.2]
      )
  
  sankey.add(
      flows = [12192, -4250, -7942],
      orientations = [0, 0, -1],
      labels = [None, None, 'Conversion Losses'],
      pathlengths = [-.2, -.2, 0.4],
      # trunklength = 1.0,
      prior = 0,
      connect = (0, 0))       # denotes which flow index from the prior to connect to which flow index in this one
  
  sankey.add(
      patchlabel = 'Gross Generation\n4250 TWh',
      flows = [4250, -1418, -1266, -1017, -8.79, -541],
      orientations = [0, 0, -1, 1, -1, 1],
      labels = [None, 'Residential', 'Commercial', 'Industrial', 'Transportation', '?'],
      prior = 1,
      pathlengths = [0.2, 0.2, 0.2, 0.2, 0.7, 0.2],
      # trunklength = 2.5,
      connect = (1, 0)
  )
  
  
  plt.savefig('./Global_Electrical_Energy_Prod_Cons_2005.png', 
                  dpi = 300, 
                  frameon = None,
                  transparent = True,
                  scale = 0.0001)
  sankey.finish()
  plt.show()
  </code></pre>
  
  <p>The expected result saved from <code>Python.app</code> launched by <code>plt.show()</code>.</p>
  
  <p><a href="https://i.stack.imgur.com/TagRg.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/TagRg.png" alt="The expected result (saved from Python.app)"></a></p>
  
  <p>The baffling result (edit: this was scrambled but it was because it was set to 300 dpi still, using the default let stackoverflow display it properly). I just tried <code>.pdf</code> and <code>.svg</code> and got the same results. </p>
  
  <p><a href="https://i.stack.imgur.com/CkLwn.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/CkLwn.png" alt="The result of the save line"></a></p>