Injecting base directory to RDiscount Markdown conversion

Question

I am using Ruby's RDiscount to convert markdown to HTML.

The markdown documents contain links (or images) that are relative to the path of the markdown file itself.

Is there a way for me to tell RDiscount that it should prepend all relative links with a string (folder) of my choice?

I am trying to achieve an effect similar to how GitHub shows images in README - where the files are looked for in the same directory as the README.

Here is an example code:

require 'rdiscount'

markdown = "![pic](image.png)\n\n[link](somewhere.html)"

doc = RDiscount.new(markdown)
# I would like to do something here, like:
# doc.base_link_path = 'SOMEFOLDER'
html = doc.to_html
puts html

# actual output => 
#  <p><img src="image.png" alt="pic" /></p>
#  <p><a href="somewhere.html">link</a></p>"

# desired output => 
#  <p><img src="SOMEFOLDER/image.png" alt="pic" /></p>
#  <p><a href="SOMEFOLDER/somewhere.html">link</a></p>"

I looked at the RDiscount class documentation but did not find anything like this.