title: BytesIO replaces transparency in PNG files with black background
body: <p>I want to keep transparent background at my 'image' variable. </p>
  
  <p>If I write into a file, image looks fine. I mean image has a transparent background.</p>
  
  <pre><code>with urllib.request.urlopen(request) as response:
       imgdata = response.read()
       with open("temp_png_file.png", "wb") as output:
           output.write(imgdata)
  </code></pre>
  
  <p>However, if I keep the image data in BytesIO, transparent background becomes a black background. </p>
  
  <pre><code>with urllib.request.urlopen(request) as response:
       imgdata = response.read()
  ioFile = io.BytesIO(imgdata) 
  img = Image.open(ioFile)
  img.show()
  </code></pre>
  
  <p>(Above code piece, img.show line shows an image with black background.) </p>
  
  <p>How can I keep a transparent image object in img variable ?</p>