If you have a ton of images to edit, perhaps consider a batch-editing program to do the work for you. Here are the best tools for batch-editing images in Windows.
gThumb is an application to view and organize images; however, you can also use it to batch resize images. Here’s how to perform batch resizing on Ubuntu.
If you want to resize multiple images in one go on your Mac, you can do so using the built-in Preview app. Here’s how it’s done.
While there are tons of applications that you can use to batch resize images, nothing beats the command line to get things done quickly and efficiently. In Mac, you can easily batch resize images with this command.