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Mac Productivity: Quick Scripts and Workflows - Scaling Images in the Finder

There are tons of apps that allow you to manipulate images on your Mac.  iPhoto and Preview are two from Apple, and there are lots more available from the Mac App Store and third-party software vendors.  What you may not know, however, is that you don’t need a third-party app to do some basic image manipulations with your existing operating system.  Using Automator, you can create your own custom image processing plug-ins, which you can run right within the Finder.

Building these workflows is pretty simple, and can often be done using only a single Automator action or two.  Let’s take a look.  The following steps walk through the creation of a workflow that scales selected images to 50%.  You might use such a workflow to prepare images for your website or blog, or to share with a friend.

1. Launch Automator (in /Applications)

2. When prompted to choose a type of workflow, select Service and click Choose

Creating an Automator Service workflow

3. Set the popup menus at the top of the workflow area to receive image files in the Finder

Setting the Service to process image files in the Finder

4. Search for the Scale Images action, and drag it to the workflow area.  When you do this, Automator displays an alert, indicating that the action will change the the image files it receives, and that these changes cannot be undone.  Automator suggests inserting a Copy Finder Items action first, to back up your files, and gives you the option to automatically insert it into the workflow.

Automator suggests working with copies of your image files prior to performing undoable actions

5. Since you probably don’t want to scale your images without being able to revert back to the originals, click Add to cause Automator to insert the Copy Finder Items action prior to the Scale Images action.

The newly inserted Copy Finder Items and Scale Images actions

The Copy Finder Items action “links up” with the header, telling you that the action receives input.  When the workflow runs, any selected image files in the Finder are automatically passed to this action for processing.  The Copy Finder Items action also links up to the Scale Images action.  This shows that the copied images are passed to the Scale Images action for processing, leaving your original images untouched.

6. From the To popup in the Copy Finder Items action, select Other... When prompted, navigate to the Desktop and click New Folder to create a new folder.  Name the new folder Scaled Images, click Create, and then click Choose.

Choosing an output folder for the Copy Finder Items action

Creating a Scaled Images folder on the Desktop

7. Configure the Scale Images action to scale images By Percentage to 50 percent.

8. Click Options beneath the Scale Images action, and select the Show this action when the workflow runs checkbox

The complete workflow 

9. Save the workflow, and name it Images • Scale by Percent

Saving the Automator workflow as a Service

Automator installs the workflow into the appropriate location on your hard drive (into the ~/Library/Services folder), and enables it.  To run the workflow, select one or more images in the Finder.  Then, choose Finder > Services > Images • Scale by Percent from the menu bar.

Running the workflow from the menu bar

Or, Control+Click on the selected items, and choose Services > Images • Scale by Percent from the contextual menu.

Running the workflow from the Finder’s contextual menu

The workflow begins running.  The selected images are copied into the Scaled Images folder on your Desktop.  Next, the Scale Images action’s interface appears, allowing you to adjust the scaling amount, if desired.

Adjusting the scaling amount

The images are then scaled according to your specifications.

Scaled images, post-processing

For more on AppleScript and Automator, check out my book  Automator for Mac OS X: Visual QuickStart Guide, as well as my video podcast series Mac Automation Made Simple.