If you need to remove an image’s background on your Mac—so that the background is transparent—you could use something like Adobe Photoshop or GIMP. The problem is, Photoshop isn’t cheap, and both applications come with a sizable learning curve. Luckily, you can remove image backgrounds with Preview for free.
Option One: Use Instant Alpha
If your image has a simple background, the easiest way to remove it is the Instant Alpha tool. Open your image and click the toolbox icon on the right end of Preview’s toolbar. This will open the editing toolbar, with a number of options.
The Instant Alpha tool resembles a magic wand, and can be found on the left side of the editing toolbar.
When you use Instant Alpha, click anywhere on the background and drag the mouse pointer. As you do this, more and more of the image’s background will be highlighted in red.
Be careful with this tool. Too much Instant Alpha and the selection area can bleed into your image. You want to select just enough so that only background detail is highlighted.
Once you’re ready, release the mouse button and your area will be selected.
Next hit the “Delete” key. If your image first needs to be converted to PNG, you’ll see the following dialog. Just click “Convert” to proceed.
Once you do, the highlighted background will be removed.
You can use the Instant Alpha multiple times on multiple areas to clean up the image completely, though it’s very inexact.
This works best on computer-generated graphics as opposed to photos, but can come through in a pinch if your photo is simple enough. It can also be used in conjunction with the Selection Tools, which we’ll describe in the next section.
Option Two: Use the Selection Tools
Let’s say you want something more precise, or your photo has a complex background that doesn’t work well with Instant Alpha. For example, here’s a perfect one of a certain uncle’s favorite niece!
Next, click the toolbox icon on the right end of Preview’s toolbar.
This will open the editing toolbar from which you want to click the “Selection Tools” and then the “Smart Lasso” from the resulting dropdown menu.
To achieve consistent results, you might want to also zoom in on your subject matter a little bit using the keyboard shortcut Command+Plus (use Command+Minus to zoom out).
Take your time and work in small sections. There’s no reason to rush.
Move the mouse pointer along the edge of your image slowly and then drag the pointer away from the edge to create an area enclosed in red, as shown in the following screenshot.
Release the mouse button, and you’ll then be left with a selected area as seen below.
Next hit the “Delete” key and convert to PNG if prompted. Your image’s background will now have an area which has been deleted.
Note, if at any point you make a mistake or want to try to get a more exact results, simply use the Undo command accessible from the “Edit” menu or by pressing Command+Z on your keyboard.
As you proceed around your image, you will notice that the Smart Lasso tool might leave bits of background behind. To clean these areas up, you can use the Lasso Selection tool, found on the Selection Tools menu.
Simply draw the Lasso around the area you want to erase and hit the “Delete” key …
… and voila, the offending area is removed.
Okay, but what about all that extra background that’s still in the picture? Use the rectangular selection tool, enclose the area you want to affect, and again, hit the “Delete” key.
As you can see, our photo is starting to come along.
It’s important to point out that this probably seems pretty tedious, and it can be, but editing an image in this way is a painstaking process, requiring patience and a steady hand.
But, you can achieve fairly nice results in a short amount of time, though the more careful you are, the better it will turn out. If you’re using a laptop and the trackpad seems a little too inexact, try switching to a mouse.
This method works well if the background is fairly complex, consisting of various textures and colors without a lot of contrast.
Option Three: Remove a Portion of an Image Using Smart Lasso
If you just want to remove a small portion of an image, such as a face, from its background, then you can use the Smart Lasso tool and the crop function.
First find a face you want to extract.
Select the Smart Lasso tool and carefully draw around the subject.
Release the mouse button and then click the crop button that appears on the toolbar or press Command+K on your keyboard.
Again, if you haven’t yet converted to PNG, you’ll be required to do so before you can proceed.
Remember, if at first you don’t succeed, press Command+Z and try again.
That’s it, you now have removed a face from it’s background (and body) in just a few short minutes. If desired, you can further clean up the image’s edges using the Smart Lasso and Lasso Selection tool as described in option two.
Once you’ve removed your image’s background, you can paste onto another background.
This makes it easy to create graphics for webpages, greeting cards, slideshows, and pretty much anything else you can think of that requires a transparent image overlaid onto a custom background.
Once you get the hang of it, you will find it’s quite easy and actually a lot of fun. Then, you can let your imagination run wild!
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