Apple's Preview program can be used to quickly convert any supported image or PDF into one of several formats.
Topher KesslerMacFixIt Editor
Topher, an avid Mac user for the past 15 years, has been a contributing author to MacFixIt since the spring of 2008. One of his passions is troubleshooting Mac problems and making the best use of Macs and Apple hardware at home and in the workplace.
There may be times when you might need to convert an image from one format to another on your Mac, either because of some requirement for a specific format, or to compress batches of images to save space.
Regardless of the specifics, if you need to convert images then you might find yourself considering expensive tools like Photoshop, or perhaps free open source projects like The Gimp as options for converting images; however, in doing so you will be overlooking a built-in option for doing this in Apple's included Preview program.
Preview is Apple's utility for viewing images and PDF files, and one of the options it has is the ability to export an image to a different file format. To do this, first open an image in Preview, and then follow these steps:
Choose "Export" from the File menu
Select a desired format from the drop-down menu
Supply a name and location for the new file, and click Save
By default, the format selection menu in Preview contains options for JPEG, JPEG-2000, OpenEXR, PDF, PNG (default selection), and TIFF; however, in addition you can choose from GIF, ICNS, Microsoft BMP, Microsoft ICON, Photoshop, SGI, and TGA by holding the Option key when you open this menu.
These routines can be applied to batches of images, so instead of converting one image at a time, you can apply these changes to a number of different files all at once. To do this, simply make a selection of the desired files in the Finder, right-click them, and then choose the Open option so they are all opened in the same Preview window.
Note that the images are shown in a list next to the displayed one. Click this list to bring it into focus, and then press Command-A to select all items in the list. Now choose the option to Export the images, and follow the instructions listed above.
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