Ubuntu How to use Shutter to store in files thumbnail of a website

Need help, I have a DB (updated constantly) of URLs and for each of those I need to store a thumbnail. It runs on Ubuntu AWS (cloud service) and it should run in the background(PHP). Since the thumbnail generation services "Pagepeeker","thumbalizr" ... are not free and can't handle large volumes I am trying to use Shutter:

ubuntu@:~$ shutter --web=http://www.google.com/ -o /var/www/html/thumbs/test.png -e

But Shutter requires openning a graphical interface to appear on my end. How can I do that without a graphical interface?

Thanks in advance for your help.