liquid_tags: Prepend SITEURL to src when it is an absolute path.

This is useful when the live site is hosted in a subdirectory
(e.g. http://www.foo.bar/mysite) to avoid having to repeat /mysite
every time.

liquid_tags/img.py

@@ -22,18 +22,21 @@
 
 [1] https://github.com/imathis/octopress/blob/master/plugins/image_tag.rb
 """
+import os
 import re
 from .mdx_liquid_tags import LiquidTags
 import six
 
 SYNTAX = '{% img [class name(s)] [http[s]:/]/path/to/image [width [height]] [title text | "title text" ["alt text"]] %}'
 
 # Regular expression to match the entire syntax
-ReImg = re.compile("""(?P<class>\S.*\s+)?(?P<src>(?:https?:\/\/|\/|\S+\/)\S+)(?:\s+(?P<width>\d+))?(?:\s+(?P<height>\d+))?(?P<title>\s+.+)?""")
+ReImg = re.compile(r'(?P<class>[-\w\s]+\s+)?(?P<src>(?P<scheme>[a-zA-Z]+://)?(?P<path>\S+))(?:\s+(?P<width>\d+))?(?:\s+(?P<height>\d+))?(?P<title>\s+.+)?')
 
 # Regular expression to split the title and alt text
 ReTitleAlt = re.compile("""(?:"|')(?P<title>[^"']+)?(?:"|')\s+(?:"|')(?P<alt>[^"']+)?(?:"|')""")
 
+# Attributes to keep in the emmitted img tag
+IMG_ATTRS = ['class', 'src', 'width', 'height', 'title',]
 
 @LiquidTags.register('img')
 def img(preprocessor, tag, markup):
@@ -42,8 +45,7 @@ def img(preprocessor, tag, markup):
     # Parse the markup string
     match = ReImg.search(markup)
     if match:
-        attrs = dict([(key, val.strip())
-                      for (key, val) in six.iteritems(match.groupdict()) if val])
+        attrs = {k: v.strip() for k, v in match.groupdict().items() if v}
     else:
         raise ValueError('Error processing input. '
                          'Expected syntax: {0}'.format(SYNTAX))
@@ -56,9 +58,17 @@ def img(preprocessor, tag, markup):
         if not attrs.get('alt'):
             attrs['alt'] = attrs['title']
 
-    # Return the formatted text
-    return "<img {0}>".format(' '.join('{0}="{1}"'.format(key, val)
-                                       for (key, val) in six.iteritems(attrs)))
+    # prepend site url to absolute paths
+    if 'scheme' not in attrs and os.path.isabs(attrs['src']):
+        siteurl = preprocessor.configs.getConfig('SITEURL')
+        attrs['src'] = siteurl + attrs['path']
+
+    # create tag
+    img_attrs = ['{0!s}={1!r}'.format(k, attrs[k])
+            for k in IMG_ATTRS if attrs.get(k)]
+    s = "<img {0}>".format(' '.join(img_attrs))
+    logging.error(s)
+    return s
 
 #----------------------------------------------------------------------
 # This import allows image tag to be a Pelican plugin