Most digital cameras nowadays, have resolutions that are far bigger than the normal monitor screen size. On average most point-and-shoot digital cameras have resolution anywhere from 3 megapixels to 10 megapixels. Most monitors these days have resolution of either 1024×768 or the slightly larger 1280×1024 pixels.
If you ever need to upload pictures online to a gallery or to a webpage, you will need to resize your images to fit the screen as well as reduce the image size. If you use Gimp, an image manipulation program, you can use David’s Batch Processor, a Gimp plugin to manage the resizing of multiple images in a single command.
Original source: http://ulyssesonline.com/2008/09/22/batch-resize-images-with-gimp/
To download the Batch Processor, open your Synaptic Package Manager located under System > Administration. Search for “Gimp Batch” and the result will give you “gimp-plugin-registry.” Install the package. You may need to supply the admin password to continue.
Access the batch file plugin within GIMP via the Filters > Batch > Batch Process menu.
You can select a single file or multiple images for our purposes here in this article. Just click over to the Resize tab and choose resize aspect ratio or set the absolute width and height. Click Start to begin the batch process.