Video Tutorial: Cutting Out Part Of An Image In Preview

8/19/2019
One of the most powerful tools in Preview is the Smart Lasso. You can use that to quickly cut out part of an image to create a new one with a transparent background, or insert an object from one image into another. While Preview lacks a lot of the image editing tools found in more powerful apps, the Smart Lasso is probably easier to use than similar features in expensive apps.
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Transcript:

Hi, this is Gary with MacMost.com. Let me show you how to use Preview on your Mac to cutout part of one image and insert it into another.
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So the Preview tool on your Mac is great for looking at PDF's and also images. You have a bunch of tools that you can use to manipulate those images. One of those tools is the Smart Lasso which is one of the Selection tools. It allows you to easily cutout part of an image and will actually find the edge of the image for you. Let me show you.

Let's double click on an image to open it up here in Preview. Now we can edit it by using the Markup tools. So I'll click Show Markup toolbar here. I have the Selection tools as the first tool here on the left. There are four different types of selections. You can do a rectangular selection. You can do an elliptical one to select an oval shape. You can do a Smart Lasso where you can define any selection you want. So I can slowly trace along the edge if I want. But it's going to be really hard to get something accurate there. It's going to take a lot of patience to draw it.

Smart Lasso makes this a lot easier. What it will do is instead of actually drawing a specific border for the selection it will give you this red zone where it's going to try to identify the edge. So if I click here and drag you can see it gives me this red zone and I can slowly move along and make sure I get the edge as close to the center of the red zone as possible. So I'll outline everything I want to keep here. So I'll outline me and the backpack. It's going to try and figure out where the edge is based on the pixels inside that red zone. So I'll go all the way down here to the bottom. Then I can just zip across the bottom there and up a little bit and then start on my shoulder, then along the side my face and back up along my cap until I get to the beginning. Notice how it shades in the area that it should select.

Now when I release the mouse or trackpad it's going to try and figure out where the edge is. Sometimes it's going to get it really well, like here. Other times it's not going to be as great. It's going to be a little rough sometimes but sometimes it will be extremely accurate. Now once you have the selection you can Copy it and do various things with it. Like, for instance, I can do File New From Clipboard and it will actually put a new document up there with just the selection. So this is transparent here in the background. I can Save this and this is actually great to use inside of Pages because then this is seen as a transparent area.

But if I want to paste this into an other image, so I'll double click on this one here, I can do Edit and Paste and there that image is on top of this one as a layer. I can position it. I can use the blue dots to resize it and there I go. You can do this with multiple images. So since I never go hiking without my dog, not even if I was going to the moon, I will include my dog here. Cut him out. I'll Copy there. Go back to this image and Paste, resize, and there now my dog is with me because he'll follow me anywhere.

So this could be fun to use and useful. Of course you can do a better job probably with the tools in apps like PhotoShop but Smart Lasso works well enough and it is so quick and easy that I find myself sometimes just using this one tool in Preview even when I'm using a more sophisticated image editing tool for everything else.