This should work for you:
<article class="photo">
<div style="width:100%; text-align:center">
<img src="https://mirror-api-playground.appspot.com/links/filoli-spring-fling.jpg" style="width:50%; height:50%;">
</div>
<div class="overlay-gradient-tall-dark"/>
<section>
<p class="text-auto-size">Spring Fling Fundraiser at Filoli</p>
</section>
</article>
Output: