title: How do you base-64 encode a PNG image for use in a data-uri in a CSS file?
body: <p>I want to base-64 encode a PNG file, to include it in a data:url in my stylesheet. How can I do that?</p>
  
  <p>I’m on a Mac, so something on the Unix command line would work great. A Python-based solution would also be grand.</p>