Need to Resize Images in Various Ways? Give Preview a Try
Even those of us who don’t work with graphics professionally often find ourselves needing to resize images. Perhaps you have a large square headshot, but the site to which you’re uploading requires it to be exactly 100 by 100 pixels. Or maybe you have an iPhone 13 Pro photo that’s 4032 by 3024, but you need the long side to be 1280 pixels and the short side to be 800 pixels. You might even need to cut out an 800-by-600 rectangle from a much larger image.
These tasks are easily accomplished with professional graphics apps like Photoshop, but you don’t need to pay for or learn Photoshop for a quick resizing and cropping of an image. That’s because Preview, which is built into macOS, can do many of these tasks with aplomb.
One note: You can resize images to be smaller with little or no loss of quality, but you can’t make images bigger without them looking fuzzier unless you employ specialized tools.
Shrink an Image without Changing Aspect Ratio
Let’s take our first example above. We have a square headshot that we need to upload to an account, but the site won’t accept an image larger than 100 pixels square. To shrink the image to the specified size, we’ll first make a copy in the Finder or we’ll open the file in Preview and choose File > Duplicate. Then, with the image open in Preview, we’ll choose Tools > Adjust Size, make sure “pixels” is chosen to the right of the Width and Height fields, and enter 100 into the Width field. Because Scale Proportionally is selected, Height automatically changes to 100 to match. We’ll click OK to exit the dialog and then save the file.
Shrink an Image and Crop to Different Dimensions
Let’s move on to our second example above. We have a photo of some home-baked bread loaves that we’ve taken with the iPhone, and we need to resize it to 1280 by 800 pixels before uploading it to our food blog. There are two problems: the image is much larger than we need to start, and when we try resizing it to the desired pixel count in one dimension, the other dimension is wrong.
We’ll start the same way we did before, by making a copy of the original and in Preview choosing Tools > Adjust Size. In the Image Dimensions dialog, we’ll first type 1280 into the Width field. In this example, doing that causes the Height field to change to 752, which is too small (below left). Remember, shrinking images is easy and works well, but expanding them is hard. So instead, we’ll type 800 into the Height field, which causes the Width field to change to 1361 (below right). That’s good; we’ll click OK to resize the image. It will look small, but we can zoom it back to the window size by choosing View > Zoom to Fit.