To move a selection marquee without moving the pixels contained in it, simply drag it using one of the marquee or lasso tools, making sure the tool is in the New selection state on the Options bar. You can also nudge a marquee one pixel at a time using the arrow keys on your keyboard.
To move the pixels selected by the marquee, you have to use the Move tool:
With the Move tool selected, you can just click and drag the marquee to the position where you want, or nudge it using the arrow keys. The area of the image contained in the marquee is moved.
You can also move selected pixels by Ctrl-dragging. This works with all but the Hand and vector tools.
Using the Lasso Tools
The lasso tools let you select irregularly-shaped areas. There are three lasso tools: Lasso , Polygonal Lasso , and Magnetic Lasso :
The Lasso tool lets you drag a free-form selection area:
- On the toolbox, click the Lasso tool.
- Use the Options bar to define the amount of feathering for sharp edges. Note that you can also antialias selections made with the lasso tools.
- Click and drag a free-form selection area. The s
election marquee follows the movement of your mouse as you draw:
When you release the mouse button, Photoshop closes the selection area by joining the beginning and ending points:
If you’re trying to select a complex area, it’s much easier to use one of the other lasso tools. The Polygonal Lasso tool lets you draw a selection area by defining anchor points, much like creating a dot-to-dot picture:
- On the toolbox, select the Polygonal Lasso tool.
- Define the selection area you want by clicking at each point that represents a change in curvature. Photoshop creates a marquee line from point to point, so to select an irregularly-shaped area, you can click at each point you need the selection marquee to change direction:
The Magnetic Lasso tool can virtually trace an image for you. As you drag your mouse (without holding down the button), the tool “snaps” the marquee to the edges of the foreground image based on its contrast with the background:
- On the toolbox, select the Magnetic Lasso tool.
- Use the Options bar to define feathering and select or deselect the Antialiased option.
- You can also define the settings for Width, Edge Contrast, and Frequency:
- Width refers to how close to the edge of an image (in pixels) you have to move your mouse for Photoshop to detect it when selecting. Smaller values make it easier to trace narrow areas in an image.
You can change this value as you’re tracing the selection area using the left bracket ([) on your keyboard to lower the value, or the right bracket (]) to increase the value.
- Edge Contrast is the amount of contrast necessary between elements for Photoshop to recognize the selection element you’re tracing. Generally, you can use higher values for higher-contrast elements, and lower values for lower-contrast elements.
- Frequency determines the frequency with which Photoshop adds anchor points as you move your mouse to create the selection marquee. When you hold the mouse still, Photoshop interprets the location as “correct” and adds an anchor point. If you have rough edges in your image, try increasing this value.
- Click once at the point where you want to begin defining the selection. With this tool, it’s best to use a high-contrast image, where the area you want to select differs considerably from the colors and light of the background.
- Without holding down the mouse button, drag the mouse around the area you want to select:
As you drag the mouse, Photoshop detects variations in the color and adjusts the marquee to trace the edges.
- When you’ve finished tracing the image, click the first point to close the selection marquee.
Using the Magic Wand Tool
The Magic Wand tool selects areas in an image with colors that match the area you select:
The Magic Wand tool selects pixels in an image based on color, hue, brightness, or opacity, depending on the option you select. Once you select an option, click on an area you want to select and Photoshop creates a marquee that includes all the pixels that match your selection:
- On the toolbox, click the Magic Wand tool.
- The Options bar provides four options, which you’ve already used with the Paint Bucket tool:
- Tolerance affects the precision of the Magic Wand tool—the range of colors the tool selects when you click. Photoshop takes this value and adds it to, and subtracts it from, the brightness value of the pixel you clicked on to come up with a range for determining whether other pixels match. The pixels that fall within this range are selected.
- The Antialiased check box, when selected, softens the border of the selection area.
- The Contiguous check box, when selected, causes only contiguous pixels to be selected—that is, only matching pixels that touch other affected pixels. When the check box is not selected, all pixels within the range of the Tolerance value are selected, regardless of where they are in the image.
- When All Layers is selected, takes into account all the layers in the image when making the selection.
- Click on an area of the image that contains pixels matching those you want selected. Below, the red pixels in the main flower are being selected with the Contiguous option checked, so the other flowers in the image aren’t selected:
Hold down the Shift key and continue to click to add to the selection area: