title: Invert colors when plotting a PNG file using matplotlib
body: <p>I'm trying to display a PNG file using matplotlib and of course, python. For this test, I've generated the following image:
  <img src="https://i.stack.imgur.com/kS9Kf.png" alt="Original File"></p>
  
  <p>Now, I load and transform the image into a multidimensional numpy matrix:</p>
  
  <pre><code>import numpy as np
  import cv2
  from matplotlib import pyplot as plt
  
  cube = cv2.imread('Graphics/Display.png')
  plt.imshow(cube)
  plt.ion()
  </code></pre>
  
  <p>When I try to plot that image in matplotlib, the colors are inverted:<img src="https://i.stack.imgur.com/34j6V.png" alt="Plot">  </p>
  
  <p>If the matrix does not have any modifications, why the colors in the plot are wrong?</p>
  
  <p>Thanks in advance. </p>