title: Extracting icons with imagemagick creates black stripes on transparency
body: <p>For a project of mine I'm fetching websites favicons and storing them to be displayed in a website. Sounds pretty trivial, but I have one strange issue. Almost all icons come in a .ico format, which is not very web friendly. Some icons also have different sizes in them.
  I'm using Imagemagick to convert them to PNG and extract only the 16x16 icon. </p>
  
  <p>I'm using the following command line for this:</p>
  
  <pre><code>convert source.ico -geometry 16x16 -alpha on -background none -flatten out.png
  </code></pre>
  
  <p>Unfortunately on some icons this creates some nasty horizontal black stripes in the transparent areas. Here is an example:</p>
  
  <p>This is the original icon:</p>
  
  <p><a href="http://g.etfv.co/http://www.mysqlperformanceblog.com/" rel="nofollow noreferrer">http://g.etfv.co/http://www.mysqlperformanceblog.com/</a></p>
  
  <p>This is the result:</p>
  
  <p><a href="http://img585.imageshack.us/img585/1463/65407408.png" rel="nofollow noreferrer">http://img585.imageshack.us/img585/1463/65407408.png</a></p>
  
  <p>Here it is again embedded here:</p>
  
  <p><img src="https://i.stack.imgur.com/wOPHp.png" alt="enter image description here"></p>
  
  <p>What could be wrong here? My ImageMagick is version 6.5.4-7</p>