Did you try to use similar structure inside <head>
tags:
<meta property="og:url" content="your_page" />
<meta property="og:type" content="website" />
<meta property="og:title" content="Some title" />
<meta property="og:description" content="Some description" />
<meta property="og:image" content=".../chart.png" />
If you want image of a chart placed on a page to represent this page, you can export it and save it earlier and use it as a content for an og:image
property. There are couple of pages worth seeing regarding this topic, like: http://ogp.me/, https://developers.facebook.com/docs/sharing/webmasters#testing. Also, here: https://developers.facebook.com/tools/debug/ you can see how your markup appears to the Facebook Crawler.