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Lesson 4. Working with Selections > Selecting with the Magnetic Lasso tool

Selecting with the Magnetic Lasso tool

You can use the Magnetic Lasso tool in Photoshop to make freehand selections of areas with high-contrast edges. When you draw with the Magnetic Lasso tool, the border automatically snaps to the borders between areas of contrast. You can also control the selection path by occasionally clicking the mouse to place anchor points in the selection border. (There is no Magnetic Lasso tool in ImageReady.)

You’ll now move the padlock to the center of the black oval you placed on the book cover earlier in this lesson, using the Magnetic Lasso tool to select the padlock.

Select the Zoom tool (), and click the padlock to zoom in to a 300% view.

Select the Magnetic Lasso tool (), hidden under the Lasso tool ().

Click once along the left edge of the padlock, and begin tracing the outline of the padlock by moving the magnetic lasso pointer around the outline of the padlock, staying fairly close to the edge of the padlock as you move.

Even though you’re not holding down the mouse button, the tool snaps to the edge of the padlock and automatically adds fastening points.

If you think that the tool is not following the edge closely enough (such as in low-contrast areas), you can place your own fastening points in the border by clicking the mouse button. You can add as many fastening points as you feel are necessary. You can also remove the most recent fastening points by pressing Delete for each anchor point you want to remove. Then, move the mouse back to the last remaining fastening point and continue selecting.

When you reach the left side of the padlock again, double-click the mouse button to make the Magnetic Lasso tool return to the starting point, closing the selection. Or, move the Magnetic Lasso over the starting point and click once.

Double-click the Hand tool () to fit the image on-screen.

Select the Move tool (), and drag the padlock to the middle of the black oval in the center of the notebook.

Choose Select > Deselect, and then choose File > Save.

Softening the edges of a selection

You can smooth the hard edges of a selection by anti-aliasing and by feathering.

Anti-aliasing Smooths the jagged edges of a selection by softening the color transition between edge pixels and background pixels. Since only the edge pixels change, no detail is lost. Anti-aliasing is useful when cutting, copying, and pasting selections to create composite images.

Anti-aliasing is available for the Lasso, Polygonal Lasso, Magnetic Lasso tool, Rounded Rectangle Marquee (ImageReady), Elliptical Marquee, and Magic Wand tools. (Select the tool to display its tool options bar.) You must specify the anti-aliasing option before using these tools. Once a selection is made, you cannot add anti-aliasing.

Feathering Blurs edges by building a transition boundary between the selection and its surrounding pixels. This blurring can cause some loss of detail at the edge of the selection.

You can define feathering for the marquee, Lasso, Polygonal Lasso, and Magnetic Lasso tools as you use them, or you can add feathering to an existing selection. Feathering effects become apparent when you move, cut, or copy the selection.

  • To use anti-aliasing, select the Lasso, Polygonal Lasso, Magnetic Lasso, Rounded Rectangle Marquee (ImageReady), Elliptical Marquee, or Magic Wand tool, and select Anti-aliased in the tool options bar.

  • To define a feathered edge for a selection tool, select any of the lasso or marquee tools. Enter a Feather value in the options bar. This value defines the width of the feathered edge and can range from 1 to 250 pixels.

  • To define a feathered edge for an existing selection, choose Select > Feather. Enter a value for the Feather Radius, and click OK.

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