title: Make image in picture element fit its container
body: <p>I have the following code:</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-css lang-css prettyprint-override"><code>#container {
    background: steelblue;
    width: 333px;
    height: 333px;
  }
  
  picture img {
    object-fit: cover;
  }</code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;div id="container"&gt;
    &lt;picture&gt;
      &lt;img src="http://placekitten.com/g/300/300" alt="kitten"&gt;
    &lt;/picture&gt;
  &lt;/div&gt;</code></pre>
  </div>
  </div>
  </p>
  
  <p>How can I get the picture to fill the container box?</p>
  
  <p><a href="https://codepen.io/Ciwan/pen/QaNvGa" rel="noreferrer">Here's a codepen</a>.</p>