[AUCTeX] preview-latex, tightpage and transparent background

[Juho Viitasalo]

Hey!

I'm doing an open source LaTeX to flash converter.

I have used preview-latex package to produce cropped equations. Here is 
the example .tex file.
------------------------------------------------
\documentclass{article}

\usepackage{amssymb,amsmath}

\usepackage[active, tightpage]{preview}

\begin{document}

\begin{preview}

$\sum$

\end{preview}

\end{document}
-------------------------------------------------


I convert this to pdf using pdftex. Pdf contains only the cropped 
equation. I convert this to swf (Flash format) using pdf2swf (SWFTools), 
but I notice that it has a white solid background. I would need the 
background of the pdf to be transparent. Is this possible?


Best regards,

Juho Viitasalo