title: Merge multiple png images with transparency in node.js
body: <p>I use this code to merge multiple images to one, but the transparency is gone in the result file. The background is solid black.</p>
  
  <pre><code>gm.in('convert').in('-size', '200x100')
  .in('xc:transparent')
  .in('-page', '+0+0').in('image1.png')
  .in('-page', '+100+0').in('image1.png')
  .in('-flatten')
  .write('result.png', function (err) {
      if (err) console.log(err);
  })
  </code></pre>
  
  <p>I also tried:</p>
  
  <pre><code>.in('background', 'transparent')
  </code></pre>
  
  <p>and</p>
  
  <pre><code>.in('background', 'black')
  .in('transparency', 'black')
  </code></pre>
  
  <p>Any idea how to do this?</p>