title: Sizing matplotlib savefig output to underlying image
body: <p>Im plotting some lines over a bitmap image in matplotlib. How do I make the image output by savefig the same size as the original image? I have the following code, but it still gives me a white border on the left and bottom, and the image is more than 100x100 pixels.</p>
  
  <p>You can <code>%paste</code> the code below to see what I mean:</p>
  
  <pre><code>import matplotlib.pyplot as plt
  import numpy as np
  
  plt.figure()
  plt.imshow(np.eye(100))
  plt.plot([1, 10, 20, 30, 40], [5, 100, 5, 100, 3], lw=3)
  plt.ylim(0,100)
  plt.xlim(0,100)
  plt.axis('off')
  plt.savefig('test.png', bbox_inches='tight', pad_inches=0)
  </code></pre>