title: wordcloud words not fitting to mask
body: <p>I'm attempting to create a wordcloud from a dataframe, where there is a column of words and a column for their respective frequencies. I've also downloaded an image that I want to use as a mask, for example: <a href="http://simpleicon.com/wp-content/uploads/cloud.png" rel="nofollow noreferrer">cloud image</a></p>
  
  <p>I can't get the wordcloud to fit to the mask - despite following the examples shown. Here is my code:</p>
  
  <pre><code>from PIL import Image
  import pandas as pd
  import numpy as np
  from wordcloud import WordCloud
  import matplotlib.pyplot as plt
  
  df = pd.DataFrame({'word':['time', 'car', 'Peter\'s', 'sky', 
                             'something', 'computer', 'brain', 'plants',
                             'trees', 'Alien\'s', 'gun', 'eat'],
                     'freq':[24, 16, 16, 15,
                             14, 13, 12, 10,
                             9, 9, 5, 3]})
  
  words = ' '.join(df['word'])
  
  cloud_image = r"C:\Users\L\Documents\Python Scripts\cloud.png"
  
  mask = np.array(Image.open(cloud_image))
  
  wordcloud = WordCloud(max_words=2000,
                        width=1280, 
                        height=720,
                        mask=mask)
  
  wordcloud.generate_from_frequencies()
  
  fig, ax = plt.subplots(figsize=(8, 6))
  ax.imshow(wordcloud, interpolation='bilinear')
  ax.axis("off")
  ax.imshow(mask, interpolation='bilinear')
  plt.show()
  </code></pre>