title: Return image in HTTP response
body: <p>After compute the scatter plot with</p>
  
  <pre><code>plt.scatter(...)
  </code></pre>
  
  <p>I can preview the graph with</p>
  
  <pre><code>plt.show()
  </code></pre>
  
  <p>However, I wish to save the plot with some sort of function like savefig() which store the image in a variable instead of a file, then return the variable in http response as content/png in django web framework</p>