[elcritch]

The main size is dealing with libxml, but that's readily handled by smaller xml libraries [http://pugixml.org]. I mean, maybe you don't want to do SVG on an arduino.

Directly comparing SVG and PNG libraries purely based on library size is misleading. PNG's aren't layered, don't contain semantic information, etc. For me librsvg is lightweight since its way better than installing phantomjs as I have been doing to generate embedable PNGs for documents.