Quite often, I find myself with a number of images (screenshots, typically) that I’ll want to convert from one format to another. If you search the Mac App Store, there are probably 300 apps that will let you do this; many are probably free. You could also use Automator, which has some good image conversion abilities, but can’t (for example) specify the quality of a JPEG conversion.
But the best way I’ve ever found is to use a tool that’s been included with every copy of macOS since the release of Mac OS X 10.3 (Panther) in October of 2003: A command line tool called sips. Yes, it requires using Terminal, but it’s quite easy to use. sips can modify one file, or any number of files, converting from one format to another. You can also use
Basic usage of sips is straightforward. (The following is written for Terminal neophytes, so apologies for any over-explaining). Assume you have an image named Beach party.tiff that you’d like to convert into a smaller JPEG, but with a relatively high quality setting. Here’s how you’d do it using sips:
- Open Terminal, in Applications > Utilities.
- Type cd, then press the Space Bar, then drag in the folder that contains the image(s) to be converted. (Alternatively, you can use this tip to directly open the selected Finder folder in Terminal.)
- Type this, then press Return: sips -s format jpeg -s formatOptions 80 "Beach party.tiff" --out "Beach party.jpg"
When you press Return, sips will convert your image file—and it’s really fast, even on larger files. The formatOptions item lets you set the quality of the JPEG in either percentage (as I used), or you can use words: low, normal, high, or best. Hopefully obviously, you specify the new filename after the --out string.
Note that the filename is enclosed in quotes. Those quotes are required, otherwise any spaces in your filenames will cause the command to break.
The real power of sips isn’t in converting one file, though; it’s in batch converting many files. Here’s how to do that…