title: Fast way to get image dimensions (not filesize)
body: <p>I'm looking for a <strong>fast</strong> way to get the height and width of an image in pixels. It should handle at least JPG, PNG and TIFF, but the more the better. I emphasize <em>fast</em> because my images are quite big (up to 250 MB) and it takes soooo long to get the size with ImageMagick's <code>identify</code> because it obviously reads the images as a whole first.</p>
  
  <p>Preferably, I look for a way that works well in Ruby, or even in Rails 3.</p>
  
  <p>I know the theory stuff (various image formats, their headers and their differences, and so on). Indeed, I ask for some kind of library that can resolve my issue in a fairly generic way.</p>
  
  <p>I just found <a href="https://rubygems.org/gems/imagesize/" rel="noreferrer">imagesize</a> which looks promising although development seems to be dead.</p>