title: How do I use PNGs to mask the edges of an image?
body: <p>I've used border-image with PNGs to create rough borders but I'm wondering if there is there a way to mask in a similar way?</p>
  
  <p><a href="http://www.rumchata.com/" rel="nofollow noreferrer">http://www.rumchata.com/</a></p>
  
  <p>Rumchata does what I'm looking for. The blue gif in the background has rough edges. I assume they're using PNG textures to mask the edges of the gif.
  Does anyone know how?</p>