Add this meta data to your html page
between <head> ... </head>
<meta property="og:title" content="Markdown Slide" />
<meta property="og:type" content="article" />
<meta property="og:url" content="http://dev.im-bot.com/slide/" />
<meta property="og:image" content="http://dev.im-bot.com/public/opengraph_logo.png" />
<meta property="og:description" content="Remark.js - easy and simple slide" />
<meta property="og:site_name" content="botbotbot" />
<meta property="og:locale" content="th_TH" />
Then using Open Graph Object Debugger to look what it look like when shared.
og:image
always cache in fb server. you should change your image url to force fb reload your image.Add this line in your _includes/head.html
between <head> ... </head>
<meta property="og:title" content="Sharing with Open Graph" />
<meta property="og:type" content="article" />
<meta property="og:url" content="http://dev.im-bot.com/opengraph//" />
<meta property="og:image" content="http://dev.im-bot.com/public/img/open-graph-thumbnail.png" />
<meta property="og:image:width" content="862" />
<meta property="og:image:height" content="453" />
<meta property="og:description" content="Make your site look pretty when sharing on facebook." />
<meta property="og:site_name" content="botbotbot" />
<meta property="og:locale" content="th_TH" />
Create _includes/opengraph.html
<meta property="og:title" content="Sharing with Open Graph" />
<meta property="og:type" content="article" />
<meta property="og:url" content="http://dev.im-bot.com/opengraph//" />
<meta property="og:image" content="http://dev.im-bot.com/public/img/open-graph-thumbnail.png" />
<meta property="og:description" content="Make your site look pretty when sharing on facebook." />
<meta property="og:site_name" content="botbotbot" />
<meta property="og:locale" content="th_TH" />
Update _config.yml
logo: /public/logo.png
locale: th_TH
Custom Post
----
excerpt: summary
thumbnail: /public/thumbnail_for_your_post.png
----