title: Get image dimensions using Refile
body: <p>Using the <a href="https://github.com/refile/refile" rel="noreferrer">Refile</a> gem to handle file uploading in Rails, what is the best way to determine image height and width during / after it has been uploaded? There is no built in support for this AFAIK, and I can't figure out how to do it using MiniMagick.</p>