title: How to change picture background color using ImageMagick?
body: <p>I want to change my picture background color, This is my source <a href="http://cdn.mayike.com/emotion/img/attached/1/image/dt/20170916/18/20170916180007_833.png" rel="noreferrer">http://cdn.mayike.com/emotion/img/attached/1/image/dt/20170916/18/20170916180007_833.png</a>.<br><br>
  If I want to change the background color to another color, what should I do?<br><br>
  If I want to change the background color to transparent, what should I do?<br><br></p>
  
  <p>I tried using <code>convert aa.png -background '#0e0e0e' bb.png</code>, but that doesn't  work.</p>