Resizer is a little tool written in Perl by Sandro CAZZANIGA, based on Imager. It takes pictures to resize them at a size, and it can handles as pictures as you have in one time.
For example:
$ resizer JPG 1024x768 # will resize all of the picture .JPG in 1024x768 inside $(pwd) ;)Under the GPLv3+, enjoy it!