title: How to detect the zoom factor of an image
body: <p>I read the related question on this topic here: <a href="https://stackoverflow.com/questions/560316/how-to-detect-subjective-image-quality">How to detect subjective image quality</a></p>
  
  <p>I would like to detect whether the uploaded image by the user could be zoomed in at high % (say, 500%) and still be or good image quality. I understand that "good image quality" is subjective, but for my purpose I would say it means "whether the image is pixelated?". I'm trying to find ways of how to do that? </p>
  
  <ul>
  <li>Should I calculate the size of the uploaded image? Higher the size, more zoomed in it can be? </li>
  <li>Should I calculate the total pixel count of the image? </li>
  <li>Should I read the metatags of the uploaded image? </li>
  <li>Combination of multiple things?</li>
  </ul>
  
  <p>Are there solutions/libraries out there that determine the <a href="http://umagowrishankar.files.wordpress.com/2012/11/spot_pixelated_new.gif" rel="nofollow noreferrer">bad pixelation</a> of an image?</p>