title: Bootstrap: button with image inside, remove visible button parts
body: <p>I have the following html:</p>
  
  <pre><code>&lt;br/&gt;&lt;br/&gt;&lt;center&gt;
    &lt;button&gt;
      &lt;img src="https://www.abeautifulsite.net/uploads/2014/09/menu-icon.png?width=600&amp;key=4bc015049071e7e16c61decfe5eca75cd081194e39a9e235b780ce644ef7e6ce"/&gt;
    &lt;/button&gt;
  &lt;/center&gt;
  </code></pre>
  
  <p>and css:</p>
  
  <pre><code>button  {
    width: 80px;
    height: 90px;
  }
  
  img  {
    width: 80px;
    height: 90px;
  }
  </code></pre>
  
  <p>which results in <a href="https://codepen.io/anon/pen/MPjVrv" rel="nofollow noreferrer">this</a>. There are edges of the button visible. Is there a way to make them invisible/expand the image to all of the button?</p>