title: Show grayscale OpenCV image with matplotlib
body: <p>I use opencv3 of python installed it by anaconda using:<br>
  <code>
  conda install -c menpo opencv3=3.2.0
  </code></p>
  
  <p>But when i use it to convert a picture to grayscale, like:  </p>
  
  <pre><code>import cv2
  import matplotlib.pyplot as plt
  
  %matplotlib inline
  
  image = cv2.imread('opencv_logo.png')
  
  image1 = cv2.cvtColor(image, cv2.COLOR_RGB2GRAY)
  
  print (image.shape)
  print (image1.shape)
  
  plt.imshow(image1)
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/i3wcH.png" rel="noreferrer"><img src="https://i.stack.imgur.com/i3wcH.png" alt="enter image description here"></a>
  I donnot know why:</p>
  
  <p>I use windows + miniconda.
  Can anyone know why and help me ? Thanks.</p>