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Removing the Background
Photoshop Magnetic Lasso Tool, Page 1

Removing the Background > Adobe Photoshop

What this image has going for it is a very distinct edge, which makes it a perfect candidate for the magnetic lasso tool. I ruled out the background eraser because there were color variations in the background that were very similar in color to the leaf color. The duplicate channel trick wouldn't work for the same reason, and the edge is just too ragged to trace it with the pen tool. Using the magnetic lasso for the initial selection and taking a few minutes to clean up the selection in quick mask mode, I was able to isolate the leaf in this image in about ten minutes.


This image is a perfect candidate for the magnetic lasso tool.

Magnetic Lasso Tool OptionsMagnetic Lasso Tool The magnetic lasso tool detects and snaps to the edge of an object as you to trace along its outline. The Magnetic lasso tool options used for this image are shown to the right. The lasso width controls how close the edge you need to stay as you trace the image. Frequency controls how often points are laid down, and edge contrast helps you fine tune the edge detection.

As you drag along the edge of an object, the tool drops fastening points to anchor the selection.

Using the magnetic lasso tool

Here's a few helpful shortcuts you should know about working with this tool: If you get too far away from the edge, you may get a point in the wrong place. You can back up and remove points by clicking the delete key as you use the magnetic lasso tool. You can also add points manually by clicking once where you want to place a point. If you find yourself using this tool often, it's a good idea to get familiar with some of the other shortcuts on page 140 of the Photoshop 5.0 User's Guide.

Using the magnetic lasso tool

When you get all the way around your object, your cursor will change when you hold it over the first point. Clicking once will close the selection and you'll see the selection marquee surrounding the image as shown below.

The selection after using the magnetic lasso tool.

As you can see, the magnetic lasso failed to detect the object's edge around the stem area of the leaf. We can correct this fairly easily by zooming in and switching to quick mask mode.

Parts of the stem were missed using the magnetic lasso.

Continue on to the next page to learn how to clean up the selection using Photoshop's quick mask mode.

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Removing the Background > Adobe Photoshop

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