[Zope] referencing images in products

I have a product which needs to reference some icons which are part of the product. Following the usual structure, the icons are www sub-directory of the product. The dtml that wants to reference the image is in the dtml sub-directory. What's the reference mechanism? <img src="../www/image.png"> in the dtml code does not resolve to the image. Nor doe the equivalent <dtml-var ...> formulation. What should the reference be?