If you need to quickly resize a bunch of images on a Mac, you don't need to open Photoshop. There's a simple way to do it from the command line, by using the
sips command. This is the basic syntax:
sips -Z MAX_SIZE FILE_NAME
By way of example, to resize a single image to a maximum of 800px (either width or height), you'd use the following. It's important to note that this will replace the existing image, so make a copy you want to keep the original.
sips -Z 800 image.jpg
sips really comes into it's own however is for folders of images. To resize multiple images just use a wildcard (
*) selector together with the file extension (
.jpg in this case). The example below will blast through all the images in
folderName, resizing them to 1200px in a flash.
sips -Z 1200 folderName/*.jpg
Your days of batch resizing images in Photoshop will be but a distant memory.