title: why cv2.imwrite() changes the color of pics?
body: <p>I have the following piece of code:</p>
  
  <pre><code>imgs = glob.glob('/home/chipin/heart/tray.png')
  current_img = io.imread(imgs[0])
  cv2.imwrite('/home/chipin/heart/01.png', current_img[0:511,0:511])  
  </code></pre>
  
  <p>The size of picture is 512*512, after being saved, a blue picture turns yellow. It seems that a channel is abandoned. I really don't know why.</p>
  
  <p>Here is the value of current_img:</p>
  
  <p><a href="https://i.stack.imgur.com/abr5h.png" rel="noreferrer"><img src="https://i.stack.imgur.com/abr5h.png" alt="value of current_img"></a></p>