title: Converting image to grayscale on python using scikit
body: <p>I need to write a function where I convert an image represented as a numpy array to  grayscale. These are some hints below that I received. I am only allowed to use <code>skimage.color</code>. </p>
  
  <p>Some relevant hints:</p>
  
  <p>Look at the <code>skimage.color</code> subpackage for some useful conversion functions.
  By default, <code>scikit-image</code> conversion functions will return images with floating-point representations from 0-1. We don't want that; we want integer representations from 0-255. NumPy has a data type for that: <code>np.uint8</code> (for 8-bit unsigned integer). To the point above, recall that the <code>np.array</code> function takes an optional argument <code>dtype</code> to specify the type of the underlying array.</p>
  
  <p>This is what I tried: </p>
  
  <pre><code>from skimage.color import rgb2gray
  
  def to_grayscale_uint(img_array):
      original = data.img_array()
      grayscale = rgb2gray(original)
      return grayscale 
  </code></pre>