Hey there,
I am really sorry for the delay of this reply as it is a weekend for us here.
By default, Joomla article page doesn't include those Opengraph tag so that is not possible to retrieve image from the article page.
Perhaps you can try find a 3rd party plugin which can render those Opengraph meta tag for Joomla article page, so you can able to retrieve those image from the article content when you share in Easysocial.