title: scikit-image (io.imread) returns floating point array, is this already normalized?
body: <p>I'm importing grayscale images that are RGBA (4-channels) formatted using scikit-image.</p>
  
  <pre class="lang-py prettyprint-override"><code>from skimage import io
  
  example = io.imread("example.png", as_gray=True)
  print(example.shape)
  print(example)
  plt.imshow(example)
  </code></pre>
  
  <p>I was expecting to get an array with values in the range 0-255. However, I found in the docs, that the above method returns an array of (64-bit) floating points.</p>
  
  <p>Does this mean the values are already normalized (X / 255)? Or do I need to be aware of something else? Thanks in advance.</p>