title: Variable size of numpy array
body: <p>I am loading an image using <code>skimage.io.imread</code> and saving the image as numpy array. Following is the inferance:</p>
  
  <p>Original image: <code>(256x512x3)</code></p>
  
  <p><a href="https://i.stack.imgur.com/XPebw.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/XPebw.jpg" alt="enter image description here"></a></p>
  
  <p>Following is the code that I execute:</p>
  
  <pre><code>img = io.imread(img_file) # 48.1 kB
  i1, i2 = img[:, :256], img[:, 256:]
  np.save('i1', i1) # 196.7 kB
  np.save('i2', i2) # 196.7 kB
  final_image = np.empty([1, 2, 256, 256, 3])
  final_image[0, 0], final_image[0, 1] = i1, i2
  np.save('final', final_image) # 3.1 MB
  </code></pre>
  
  <p>Can anyone explain why such a huge difference in the size of the image?</p>
  
  <p>EDIT: dtype of <code>i1</code>, <code>i2</code>, <code>final_image</code> is <code>np.float64</code></p>