swfmill is an xml2swf and swf2xml processor with import functionalities.

It's most common use is the generation of asset libraries containing
images (PNG and JPEG), fonts (TTF) or other SWF movies for use with MTASC-
or haXe-compiled ActionScript, although swfmill can be used to produce
both simple and complex SWF structures.

* built around an XSLT/EXSLT processor (libxslt)

* input and output of the XSLT transformation can be either XML or binary SWF

* XSLT commands for importing PNG, JPEG, TTF and SWF, and for mapping SWF ID
  numbers

* built-in "simple dialect" to support library creation and building simple
  SWFs
