XSL Extensions with xsl:script and Saxon?

Hi,

I am thinking of some extensions for the saxon parser to use with xsl:script

For example i would like to get img width and height via an extension 
everytime my stylesheet inserts an img tag in the output tree.

This would be very fine if you use many graphical buttons for navigation. You 
could use a chapter id add a ".gif" an put in the src attribute. And you dont 
have to care about the height and width because the extension gets it for you.

On the other hand you could create images on the fly. 
imagine some xml tag like this:

<button label="Home"/>

and then your  button template inside your xsl is calling an extension (maybe 
gimp), rendering the image, returning width and height.

Are there any solutions available already?
If not, is it possible to connect Saxon and Perl (because Perl can connect to 
anything :-) ? 
Wouldnt it be fine if you could make a system call from inside of an xsl 
stylesheet (and via this way you could call any programm you like...)?

regards,
janning

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