title: Display image as grayscale using matplotlib
body: <p>I'm trying to display a grayscale image using <code>matplotlib.pyplot.imshow()</code>.  My problem is that the grayscale image is displayed as a colormap.  I need it to be grayscale because I want to draw on top of the image with color.</p>
  <p>I read in the image and convert to grayscale using PIL's <code>Image.open().convert(&quot;L&quot;)</code></p>
  <pre><code>image = Image.open(file).convert(&quot;L&quot;)
  </code></pre>
  <p>Then I convert the image to a matrix so that I can easily do some image processing using</p>
  <pre><code>matrix = scipy.misc.fromimage(image, 0)
  </code></pre>
  <p>However, when I do</p>
  <pre><code>figure()  
  matplotlib.pyplot.imshow(matrix)  
  show()
  </code></pre>
  <p>it displays the image using a colormap (i.e. it's not grayscale).</p>
  <p>What am I doing wrong here?</p>