title: matplotlib savefig() plots different from show()
body: <p>When I use <code>show()</code> to plot the graphs in <code>X</code>, the graphs looks very good. However when I start to use <code>savefig()</code> to generate large amount of graphs, the <code>savefig()</code> generated graphs
  ' font, lines, polygons all look smaller than the <code>show()</code> generated graph. My environment is Ubuntu and the backend for <code>show()</code> is <code>Qt4Agg</code>. How can I make the <code>show()</code> plot and the <code>savefig()</code> plot looks consistent?</p>