Absolute path for OG

sitegin/nunjucks.js

@@ -7,6 +7,7 @@ var nunjucks = require('nunjucks');
 var fs = require('fs');
 var dateFilter = require('nunjucks-date-filter');
 var util = require('util');
+var url = require('url')
 
 var config = require('./config');
 console.log('watch: '+config.watch);
@@ -50,6 +51,10 @@ env.addFilter('relURL', function(filename, dir){
   return dir+'/'+filename;
 })
 
+env.addFilter('absURL', function(rel, base){
+  return url.resolve(base, rel)
+})
+
 var formats = {};
 
 module.exports = function(data, type, config) {

theme/templates/article.html.nunj

@@ -4,7 +4,7 @@
 
   <meta property="og:type" content="article" />
   <meta property="article:published_time" content="{{ metadata.date.creation }}" />
-  <meta property="og:image" content="{{ metadata.image }}" />
+  {% if metadata.image %} <meta property="og:image" content="{{ metadata.image | absURL( canonicalURL ) }}" /> {% endif %}
   <meta property="og:description" content="{% if metadata.perex %}{{metadata.perex}}{% else %}{% if metadata.perex_e %}{{metadata.perex_e | truncate}}{% else %}{% if content %}{{ content | striptags | truncate }}{% endif %}{% endif %}{% endif %}" />
 
 {{ super() }}