title: RMagick looses transparency when saving gifs
body: <p>I am trying to wite a Ruby script for batch processing images with RMagick. But when I use for exaple this code:</p>
  
  <pre><code>img = ImageList.new('in.gif').first
  pixels = img.get_pixels(0,0,img.columns,img.rows)
  img.store_pixels(0,0, img.columns, img.rows, pixels)
  img.write('out.gif');
  </code></pre>
  
  <p>I expect my image stay unchanged, but it looses it's transperency turning it into black. How do I correctly process gifs with transparency with RMagick?</p>
  
  <p>EDIT:
  Here is my image:
  <a href="http://i.imgur.com/uYL6vAR.gif" rel="nofollow">http://i.imgur.com/uYL6vAR.gif</a></p>
  
  <p>If it's usefull the virsion I used are:
  Rmagick gem - 2.13.2
  Ruby - 2.1.2
  ImageMagick 6.7.7-10
  Ubuntu 13.10</p>
  
  <p>EDIT2:
  I found that this actually doesn't occur for all my images but rather for that exactly image and other of this small size. Maybe something is wrong with processing small gifs?</p>