Relative paths in Flying Saucer XHTML?

Question

I am using Flying Saucer to render some PDF documents from strings to XHTML. My code is something like:

iTextRenderer.setDocument(documentGenerator.generate(xhtmlDocumentAsString));
iTextRenderer.layout();
iTextRenderer.createPDF(outputStream);

What I'm trying to understand is, when using this method, where are relative paths in the XHTML resolved from? For example, for images or stylesheets. I am able to use this method to successfully generate a text-based document, but I need to understand how to reference my images and CSS.