title: Verifying a remote image is actually an image file in ruby?
body: <p>I'm trying to figure out how I can verify what I'm feeding into carrierwave is actually an image.  The source I'm getting my image urls from isn't giving me back all live urls.  Some of the images no longer exist. Unfortunately it doesn't really return the right status codes or anything because I was using some code to check if the remote file exists and it was passing that check.  So now just to be on the safe side I'd like a way to verify i'm getting back a valid image file before I go ahead and download it. </p>
  
  <p>Here is the remote file checking code I was using just for reference but I'd prefer something that actually can identify that the files are images.</p>
  
  <pre><code>require 'open-uri'
  require 'net/http'
  
  def remote_file_exists?(url)
      url = URI.parse(url)
      Net::HTTP.start(url.host, url.port) do |http|
        return http.head(url.request_uri).code == "200"
      end
  end
  </code></pre>