For those that care, here is basically how the service works.  The filter
is applied to an SVG, and the uploaded graphic is converted to SVG using
the following process:

EPS -> PDF -> SVG
PDF -> SVG
SVG -> PDF -> SVG

where the EPS -> PDF conversion is done with the standard `epstopdf`
included with TeX.  The PDF -> SVG conversion is done with `pdf2svg` which
is available from

http://www.cityinthesky.co.uk/opensource/pdf2svg

and which uses Cairo and Poppler for its conversion.  Now in order for my
simplistic filter to function, all SVG's must essentially "look alike"
(i.e., come from the same source).  Therefore, uploaded SVG's are converted
to PDF (using Inkscape) and then back to SVG (using `pdf2svg`).  The filter
then works with the resulting SVG and converts it back to the uploaded
format using Inkscape.

Troy