Many people don’t realize that every copy of OS X ships with a robotic personal assistant: Automator.

Automator is a drag and drop tool that allows you to quickly throw together time saving mini applications.

Something many people need to do is to repeatedly convert photos from one size or format to another, and while it’s easy enough to use Photoshop or another dedicated graphics tool to repeatedly Open > Save As > Close files it’s far from efficient.

Step 1: Find Automator

Automator is the application with the icon that looks like a rejected Wall-E case study (in your /Applications folder). Double click him to get started.

Step 2: Choose What To Modify

You’re going to want to drag and drop actions from the left side of the application onto the right “workflow” side of the application. Like gravity, reading and our current economic system, the actions will proceed from top to bottom.

As we’re going to be working with images, it may be tempting to choose the “Ask for Photos” action from the list. Don’t do it as the action should probably be titled “Ask for iPhoto images” as it’s not possible to just get a folder full of images to deal with.

Instead choose: “Ask for Finder items”, which is used for manipulating any combination of files and folders.

Step 3: Choose your Manipulations

From here you can drop in any type of image manipulation technique that you need: scaling, cropping, and thumbnailing are all options that both sound vaguely dirty and are available in Automator. Additionally, “Change Type of Images” will likely come in handy.

If you’d like to see all the options that are available, type “images” into the search box and read the descriptions.

Step 4: Test your Automation

Click the “Run” button in the upper right corner to begin processing. It’s a good idea to back up your files while you’re tweaking things to be just right as you’ll likely dramatically trash a few sets of images while you’re getting things right.

Step 5: Save your Automation as an Application

While you can save your Automation as either a “Workflow” (which will re-open Automator when run) or as an Application, I’d highly recommend saving as an application as it opens up a further world of possibilities: running jobs periodically with cron, distributing the workflow to non technical users, or even adding a cool icon and attempting to sell the application as your own batch processing tool.