I want the script to be able to take an argument from
command-line ( site URL , ex:www.google.com ) and return a
picture of the website , a thumbnail image .

You don't really want a screenshot, then, since there's no screen. You want to render the Web page to a thumbnail image.

I don't have any good advice for doing that, but maybe that will give you some new keywords to google. :-)

Good luck!


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