GS-PS: Photoshop: GS-PS: Selecting

Review of Layers

Selecting Parts of Your Image

In some cases, you may wish to isolate part of an image for editing, or to combine it with other images. In Photoshop, this is called a selection. When part of an image has been selected, the image editing tools and commands work the same way, but only the selected part of the image is affected.
When you make a selection, the part of the image that is protected (that is, not selected) is sometimes referred to as a mask. Just as you might use masking tape to protect part of a wall when you are painting a room, in Photoshop you are masking the part of the image that you want to protect when you have selected part of an image for editing.
When you make a selection, a selection outline appears to show you the selected area. In the following example, a rectangular area has been selected:

Note: In some cases, pixels may be partially selected (see feathering, below). In such a case, the selection outline is only approximate because there is no sharp boundary between selected and masked areas.

Using Selection Tools

To make a selection, click a selection tool icon in the toolbox
Take a look at the Options bar for the tool you are using. (If the options are not visible, choose Window>Options.) You may want to adjust the options for the tool (for example, to make the selection feathered).
In some cases, tools may be hidden "behind" other tools. Click and hold the tool to see the hidden tools.

The rectangular marquee tool () is probably the most frequently used selection tool. It allows you to select rectangular areas. Click and drag diagonally with it to make a selection.
The elliptical and row marquee tools are less frequently used. They are hidden "behind" the Marquee tool.
To select an elliptical area or a single row of pixels, type M to cycle through the marquee tools. Then drag (with Elliptical tool) or click (with Single Row tools) to make a selection.

To create freeform selections, you can click and drag with the Lasso tool (). But the lasso tool may not give you enough control. For more control, you may find the polygon lasso and magnetic lasso tools easier to use.
The Polygon Lasso tool () is often quite useful for selecting irregularly shaped areas. To use it, click on the image, then move to another place and click again to create a segment. Click multiple times to create a selection around an irregular area in your image. Double-click to finish the selection. Note: If you are in the middle of selecting and you make a mistake, press the backspace key to go back one segment, or click the Esc key to undo the selection entirely.
Without pressing the mouse button, move the magnetic lasso tool around an area to select it. The tool will look for edges. You can adjust its sensitivity to edges in the options bar.

Click somewhere on the image with the magic wand tool to select adjacent portions of the image based on color brightness. The higher the tolerance entered in the Options palette, the more pixels are selected.