Resizing and cropping a photo are basic photo editing features and it stands to reason that an app like Preview will have both of them. The resize feature is easy to find while the crop feature may be a bit difficult to locate. Here’s how you can crop and resize images in Preview on macOS
Crop images in Preview
We’re going to start with the crop feature since it’s a bit more elusive than the resize feature. When you open an image in Preview, it is all set to be cropped. You don’t really need to activate or select the feature to use it. All you have to do is click and drag your mouse cursor over the area you want to keep. When you drag the mouse, an outline will appear and if you look under the cursor, it will tell you the dimensions of the outline.
The sides of this outline have their central points that you can click and drag, and also use to judge what’s centered in the image that will be left once everything else is cropped out. The marquee that you draw can be dragged and repositioned as a whole on the image.
When you’re ready to crop the image, tap the Command+K keyboard shortcut, and then save the image or export it.
Resize photos in Preview
To resize a photo in Preview, go to the Tools item on the menu bar, and select Adjust Size.
In the panel that opens, make sure ‘Custom’ is selected under ‘Fit into’. You can change the unit that the image is resized in. In the Width field, enter the new size of the image you want to set. The Height should change automatically and in proportion to the change in the width that you enter. If it doesn’t, make sure the ‘Scale Proportionally’ option is enabled on this panel. Click OK to resize the image.
Generally speaking, you should always resize images proportionally. If you do not resize an image proportionally, you will end up with an image that is either stretched out along the width or height, or an image that is pinched in along the width or height.
Resizing can generally be undone in that you can revert the size of an image back to what it was before though resizing it multiple times may eventually impact its quality. Cropping is permanent. Once you cut a part of an image out, there’s no getting it back.