Parallax portfolio center image

Hi!

The images in the parallax portfolio are not centered on desktops. They are on mobile devices.
I would like them to always be centered, in any resolution.
How do I achieve this?

<section id="content">
<div class="content-wrap nopadding">
<div id="portfolio" class="portfolio portfolio-parallax clearfix">
<article class="portfolio-item pf-media pf-icons">
<div class="portfolio-image" style="background-image: url('images/home/1.jpg');" data-bottom-top="background-position:0px 300px;" data-top-bottom="background-position:0px -300px;"><div class="portfolio-overlay"></div></div>
<div class="portfolio-desc">
<h3>1</h3>
<div class="portfolio-divider"><div></div></div>
</div>
</article>
</div>
</div>
</section>

Cheers, Paul

Great! It works fine.

Thanks!