slackbuilds_ponce/graphics/gimp-plugin-bimp

With BIMP you can apply a set of GIMP manipulations on groups of images. It provides an easy to use 
interface and a lot of batch functions:

Resize, Crop, Flip and rotate, Blurring and sharpening, Color (and curve) correction, Watermark,
Rename, Change compression and format, ... and whatever you want! (almost)