Some tasks, such as changing an image file's format, are easy to do but eat up a lot of your time. In some cases, you can speed things up by using OS X’s Services — little extension tools available with just a right-click of your mouse. We’re going to build a basic Service that converts just about any image you select in Finder into the JPEG format, reducing its file size and making it ready for web use. It’s powered by Preview, meaning it can convert (and batch convert) just about any image that Preview can open.
To begin, open Automator (from the Applications folder). Create a new document, and choose “Service” as the document type, then click “Choose.” In Automator, the left side of the screen shows your available “Actions,” while the right side shows the workflow you’ve built and its options.
Make a JPEG Conversion Service
1. Start Your Workflow
At the top of the workflow on the right, change the dropdown after “Service receives selected” to “image files,” then the dropdown that says “any application” to “Finder.” Now, in the Library sub-menu on the left, choose “Photos.” In the Actions list just to the right of that, look for “Change Type of Images.” Drag this into the workflow screen and drop it anywhere.
2. Get Specific
You'll get a warning about adding a “Copy Finder Items” Action to your workflow — click “Add.” This copies the files you’ve chosen to convert to your desktop (or any folder you choose) before they’re altered, so the originals are kept safe. Now, in the “Change Type of Images” Action below this, click the menu that says “TIFF” and change it to “JPEG.” (Alternatively, you can choose a different type of image file you'd prefer).
3. Convert the Image
Use the File menu or press Command + S to save and name your Service — this is how it will appear in the right-click menu, so call it something like “Convert to JPEG.” That’s it! Quit Automator and right-click on any image file. Look at the bottom of the contextual menu and you should see “Convert to JPEG” as an option, just the way you named it. (Sometimes, it may be within a Services sub-menu.) Click it to convert. That's all there is to it!