[Typo3] How to access the width of an image in TypoScript?

[Ralf Rings]

Hello all,

could someone please tell me if it is possible to access the width-value 
of an image in TypoScript. And how its done, of course ;-)

I need this to limit the width of a container for an image-caption. The 
original Typo3 image-content is wrapped by a table with a corresponding 
width-value. Unfortunately this value is set somewhere deep inside the 
core PHP-classes... too complicated for me, to find out exactly where it 
comes from and how its accessed.

Thanks
Ralf