I would like to write a python script that takes a bunch of swf files and renders them to individual image files.
Each swf file has just one frame (text, pictures etc.)
I'm sorry to answer my own question, but I found an undocumented feature of swfrender (part of the swftools) by browsing through the sources.
swfrender path/to/my.swf -X -Y
-o
As you might have guessed the X option lets you determine the width (in pixels) of the output and Y does the same for the height. If you just set one parameter, then the other one is chosen in relation to the original height-width-ratio (pretty useful)
That does the trick for me but as Zarate offered a solution that might be even better (I'm thinking of swf to PDF conversion) he deserves the credits.
Cheers