GIMP doesn’t feature native batch functionality and as such we find ourselves turning to the excellent David’s Batch Processor extension script which plainly put, does. To get it, the easiest thing to do is head over to your Synaptic Package Manager and do a search for gimp-plugin-registry. This neat little package bundles together a whole lot of useful GIMP plugins, including the one that we’re interested in, namely David’s Batch Processor. Mark for installation and apply.
Once installed, open up GIMP and access the Filters -> Batch -> Batch Process… menu option. This will launch David’s Batch Processor and from this point onwards it is pretty simple to get going. First, select all the files or the folder containing the files that you wish to process on the Input tab. Once selected, visit the various tabs to set whatever batch operation you want to apply to the images. Obviously the resize would be the number one tab visited in this instance! 🙂