title: How to check if and image is mono color or empty?
body: <p>I need to prevent users from uploading blank profile images. For blank images I mean a full white or any other full color image.
  I think the best approach is to check if the images contains just one color but i don't know how to do it.</p>
  
  <p>I'm trying to check this after the image is uploaded, just to simplify things.</p>
  
  <p>Could anyone help me on this?</p>