Preview is a greatly under-appreciated app that has been bundled along with Mac OS X since the beginning, getting better and better with each OS X release. One quiet feature that has been around for a while is the ability to mass convert a group of pictures from one file type to another, often referred to as batch conversion. This lets you easily take a large amount of JPG files and convert them over to PNG, for example.
Batch image conversion works with any number of image files and with nearly any image formats. It’s safe to assume that if you can open the image files into Preview app, you can export them to a new file type, including GIF, ICNS, JPEG, JPEG-2000, BMP, Microsoft Icon, OpenEXR, PDF, Photoshop PSD, PNG, SGI, TGA, and TIFF.
How to Convert a Group of Image Files to a New Format with Preview
Converting large groups of image files this way is really easy in OS X, here is what you’ll want to do:
- From the Finder, select a group of images and open them all with Preview, do this either by launching the image files directly or dragging and dropping them into the Preview Dock icon
- Once the images are opened in Preview, click within the preview pane on the left side and then Select All, either by hitting Command+A or by pulling down the edit menu and choosing that option – you must select all the images to convert
- Pull down the File menu and choose “Export Selected Images…”
- Optionally, create a new folder for the converted pictures to save to, otherwise simply select the destination for the files to save to
- Now select the desired image format to batch convert all the selected image files to (you can Option-click to reveal more)
- Click “Choose” to save and begin the conversion process
A progress indicator bar will appear over the pictures letting you know things are progressing:
Depending on the amount of images selected to convert, their resolutions – which can also be resized at the same time if desired, and their file formats, this process can either be very fast or somewhat time consuming. Batch conversion of image files is usually quite speedy, but it ultimately depends on the size of the image files, the formats chosen, and the speed of the Mac.
As mentioned, the Bulk Export Images feature in Preview is supported in all versions of OS X, including OS X Yosemite, OS X Mavericks, Mountain Lion, you name it. The interface may look a tiny bit different depending on the version of system software on the Mac.
The video below walks through the group file type conversion process with Preview, taking a selection of JPG files and saving them to a new folder as PNG’s. As you may notice in the video, the original JPG files remain intact throughout this process.
The ability to convert a single image file has been around for quite some time and that shouldn’t be a mystery to those who have used Preview before, but the group conversion ability is limited to newer versions of the app in OS X.
If you follow us here at OSXDaily with regularity, you probably know that we recently showed how to perform image conversions from the command line using the sips tool as well, but using the GUI and Preview is much easier for most users and is going to have a wider appeal.