How to Use Preview on Mac to Extract a Small Image or Section From a Big Image

Alvaro Bernedo

Lasso Done MainWe’ve all been there sometime. There’s this image we want but it is part of a larger one that gets in the way. If the image is simple, like a circle or a rectangle, then it might be easy to just cut it out and paste somewhere else. But what happens if the shape is not that simple? Well, in this case unless you know advanced image editing and have Photoshop among your applications, you are done for.

Thankfully, every Mac comes with Preview, a very simple, yet powerful application that (sadly) most Mac owners only use to view images and PDF files.

Preview App

However, Preview also comes with a quite decent set of editing tools that can take care of a few complex tasks, including extracting shapes, just like with Photoshop except in a far easier way.

You want to learn how to do it? Just follow the steps below.

Step 1: Pick your image and open it on Preview. If Preview is not set as your default to open images, you can find the application in the Applications folder.

Image Open

Step 2: Choose the object you want to “extract” from the image. In this case I choose the Macbook Pro. To extract it though, we’ll first have to remove the background and the text in the image.

Step 3: On the top bar of Preview, click on the pencil icon to reveal the Edit Toolbar. From the available tools go to the Selection Tools (the dotted rectangle icon), click on it and then select Instant Alpha.

Tool Bar Open

Instant Alpha Choose

Step 4: Now press and hold on the mouse and start moving the cursor along the image. You will see that the image starts to become “reddish” at some areas depending on how you move the cursor over it. Keep doing so until everything in the image takes this red tone EXCEPT for the shape you want to extract.

In most cases, you might see that not only the shape you want to extract but also other shapes in your image don’t become red in color. Don’t worry about that and release the cursor. You will see all these shapes (including the one you want to extract) have been selected.

Selected With Instant Alpha

Step 5: With the shapes selected, press Delete and click on Convert if the dialog box pops-up. You will see that a few images and most of the background are gone by now.

Convert Option

Background Out

Step 6: Click on the Selection Tools icon again, but this time choose the Lasso Selection instead. Use it to draw a selection around all the objects that remain in your image making sure to completely close the selections. Once you are done with each, hit the Delete key again in order to remove them from your image. Your image should now be “clean”, except that it still belongs to the rest of the “frame”.

Lasso Selection

Lasso Selected

Lasso Done

Step 7: To fix this, select Instant Alpha from the selection tools and use it until everything but your image takes a red tint, then release the cursor. Everything but your image’s shape should be selected. To reverse the selection, choose Invert Selection from the Edit menu.

Invert Selection

Once done, press Command-X to cut it. The object will now be on your clipboard and ready for you you to paste it anywhere you want. In this case, in Photoshop for further retouching.

Photoshop app

Pasted in Photoshop

There it is, a quite advanced image editing technique made easy and free, all with a tool that comes included with your Mac. Make sure to try it out and experiment with Preview. It is a deceptively powerful application that is sure to surprise you.

Also See
#image editing #preview

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Alvaro Bernedo

Written By

Alvaro Bernedo

Contributor at Guiding Tech