You can find names of methods that correspond to various Gimp operations via Gimp's PDB Explorer (menu Xtns/PDB Explorer). In this case it is gimp_image_scale. According docs avialable via PDB Explorer this function expects following parameters:
In:
IMAGE image
INT32 new_width
INT32 new_height
Perl module
Gimp that provides bindings allows you to call this function as
Gimp->gimp_image_scale($img, $new_width, $new_height);
It also does some magick so you can call same operation under different names. All following calls do the same thing:
Gimp->gimp_image_scale($img, $new_width, $new_height);
Gimp->image_scale($img, $new_width, $new_height);
$img->scale($new_width, $new_height);
All you have to do is adding such call before saving jpeg file.
You can learn more from documenation in Gimp module and from Gimp-Perl web site.
--
Ilya Martynov
(http://martynov.org/)