Making Selections in Photoshop

A selection isolates one or more parts of your image. By selecting specific areas, you can edit and apply effects and filters to portions of your image while leaving the unselected areas untouched.

Photoshop provides separate sets of tools to make selections of raster and vector data. For example, to select pixels, use the marquee tools or the lasso tools. You can also use commands in the Select menu to select all pixels, to deselect, or to reselect. To select vector data, you can use the pen or shape tools, which produce precise outlines called paths (just like in Adobe Illustrator). You can convert paths to selections or convert selections to paths.

Selections can be copied, moved, and pasted, or saved and stored in an alpha channel. Alpha channels store selections as grayscale images called masks. A mask is like the inverse of a selection: it covers the unselected part of the image and protects it from any editing or manipulations you apply. You can convert a stored mask back into a selection by loading the alpha channel into an image.

Marquee tools

The marquee tools let you select rectangles, ellipses, and 1‑pixel rows and columns.

1. Select a marquee tool:

   Rectangular Marquee 

   Makes a rectangular selection (or a square, when used with the Shift key).

   Elliptical Marquee 

   Makes an elliptical selection (or a circle, when used with the Shift key).

   Single Row or Single Column Marquee

   Defines the border as a 1‑pixel‑wide row or column.

2. Specify one of the selection options in the options bar.
    
   

   
   

   Selection options

   A. New, B. Add To, C. Subtract From, D. Intersect With

   
   

3. Do one of the following to make a selection:
   • With the Rectangle Marquee tool or the Elliptical Marquee tool, drag over the area you want to select.
     
   • Hold down Shift as you drag to constrain the marquee to a square or circle (release the mouse button before you release Shift to keep the selection shape constrained).
     
   • To drag a marquee from its center, hold down Alt (Windows) or Option (Mac OS) after you begin dragging.
     
     
     

     
     

     Dragging a marquee from the corner of an image (left), and from the center of an image (right) by pressing Alt/Option as you drag
   • With the Single Row or Single Column Marquee tool, click near the area you want to select, and then drag the marquee to the exact location. If no marquee is visible, increase the magnification of your image view.
     
To reposition a rectangle or elliptical marquee, first drag to create the selection border, keeping the mouse button depressed. Then hold down the spacebar and continue to drag. Release the spacebar, but keep the mouse button depressed, if you need to continue adjusting the selection border.
Lasso Tool
The Lasso tool is useful for drawing freeform segments of a selection border.
1. Select the Lasso tool , and select options.
2. Drag to draw a freehand selection border.
3. Specify one of the selection options in the options bar (see diagram above)
4. To draw a straight-edged selection border when no other pixels are selected, press Alt (Windows) or Option (Mac OS), and click where segments should begin and end. You can switch between drawing freehand and straight-edged segments.
5. To erase recently drawn segments, hold down the Delete key until you’ve erased the fastening points for the desired segment.
6. To close the selection border, release the mouse without holding down Alt (Windows) or Option (Mac OS).

Polygonal Lasso Tool

 The Polygonal Lasso tool is useful for drawing straight-edged segments of a selection border.
1. Select the Polygonal Lasso tool , and select options.
2. Specify one of the selection options in the options bar (see diagram above)
3. Click in the image to set the starting point.
4. Do one or more of the following:
   • To draw a straight segment, position the pointer where you want the first straight segment to end, and click. Continue clicking to set endpoints for subsequent segments.
     
   • To draw a straight line at a multiple of 45°, hold down Shift as you move to click the next segment.
     
   • To draw a freehand segment, hold down Alt (Windows) or Option (Mac OS), and drag. When you finish, release Alt or Option and the mouse button.
     
   • To erase recently drawn straight segments, press the Delete key.
     
5. Close the selection border:
   • Position the Polygonal Lasso tool pointer over the starting point (a closed circle appears next to the pointer), and click.
     
   • If the pointer is not over the starting point, double-click the Polygonal Lasso tool pointer, or Ctrl-click (Windows) or Command-click (Mac OS).
     

Magnetic Lasso Tool


When you use the Magnetic Lasso tool , the border snaps to the edges of defined areas in the image. The Magnetic Lasso tool is not available for 32‑bits-per-channel images.

The Magnetic Lasso tool is especially useful for quickly selecting objects with complex edges set against high-contrast backgrounds.
1. Select the Magnetic Lasso tool.
2. Specify one of the selection options in the options bar (see diagram above)
3. Set any of these options:

   Width

   To specify a detection width, enter a pixel value for Width. The Magnetic Lasso tool detects edges only within the specified distance from the pointer.
   

   To change the lasso pointer so that it indicates the lasso width, press the Caps Lock key. You can change the pointer while the tool is selected but not in use. Press the right bracket (]) to increase the Magnetic Lasso edge width by 1 pixel; press the left bracket ([) to decrease the width by 1 pixel.

   Contrast

   To specify the lasso’s sensitivity to edges in the image, enter a value between 1% and 100% for Contrast. A higher value detects only edges that contrast sharply with their surroundings; a lower value detects lower-contrast edges.

   Frequency

   To specify the rate at which the lasso sets fastening points, enter a value between 0 and 100 for Frequency. A higher value anchors the selection border in place more quickly.
   

   On an image with well-defined edges, try a higher width and higher edge contrast, and trace the border roughly. On an image with softer edges, try a lower width and lower edge contrast, and trace the border more precisely.

   Stylus Pressure

   If you are working with a stylus tablet, select or deselect the Stylus Pressure option. When the option is selected, an increase in stylus pressure decreases the edge width.

4. Click in the image to set the first fastening point. Fastening points anchor the selection border in place.
5. To draw a freehand segment, either release or keep the mouse button depressed, and then move the pointer along the edge you want to trace. The most recent segment of the selection border remains active. As you move the pointer, the active segment snaps to the strongest edge in the image, based on the detection width set in the options bar. Periodically, the Magnetic Lasso tool adds fastening points to the selection border to anchor previous segments.
   
6. If the border doesn’t snap to the desired edge, click once to add a fastening point manually. Continue to trace the edge, and add fastening points as needed.
    
   

   Fastening points anchor selection border to edges
   
   
7. To switch temporarily to the other lasso tools, do one of the following:
   • To activate the Lasso tool, hold down Alt (Windows) or Option (Mac OS), and drag with the mouse button depressed.
     
   • To activate the Polygonal Lasso tool, hold down Alt (Windows) or Option (Mac OS), and click.
     
8. To erase recently drawn segments and fastening points, press the Delete key until you’ve erased the fastening points for the desired segment.
9. Close the selection border:
   • To close the border with a freehand Magnetic segment, double-click, or press Enter or Return.
     
   • To close the border with a straight segment, hold down Alt (Windows) or Option (Mac OS), and double-click.
     
   • To close the border, drag back over the starting point and click.
     

Quick Selection Tool

You can use the Quick Selection tool  to quickly “paint” a selection using an adjustable round brush tip. As you drag, the selection expands outward and automatically finds and follows defined edges in the image.
1. Select the Quick Selection tool .
2. In the options bar, click one of the selection options: New, Add To, or Subtract From. New is the default option if nothing is selected. After making the initial selection, the option changes automatically to Add to.
   
3. To change the Quick Selection tool brush tip size, click the Brush menu in the options bar and type in a pixel size or move the Diameter slider. Use the Size pop‑up menu options to make the brush tip size sensitive to pen pressure or a stylus wheel.
   When creating a selection, press the right bracket (]) to increase the Quick Selection tool brush tip size; press the left bracket ([) to decrease the brush tip size.
4. Choose Quick Selection options.

   Sample All Layers

   Creates a selection based on all layers instead of just the currently selected layer.

   Auto-Enhance

   Reduces roughness and blockiness in the selection boundary. Auto-Enhance automatically flows the selection further toward image edges and applies some of the edge refinement you can apply manually in the Refine Edge dialog with the Smooth, Contrast, and Radius options.

5. Paint inside the part of the image you want to select. The selection grows as you paint. If updating is slow, continue to drag to allow time to complete work on the selection. As you paint near the edges of a shape, the selection area extends to follow the contours of the shape edge.
   
   
   

   
   

   Painting with the Quick Selection tool to extend the selection
   If you stop dragging and then click or drag in a nearby area, the selection will grow to include the new area.
   • To subtract from a selection, click the Subtract from option in the options bar, then drag over the existing selection.
     
   • To temporarily switch between add and subtract modes, hold down the Alt (Windows) or Option (Mac) key.
     
   • To change the tool cursor, choose Edit > Preferences > Cursors > Painting Cursors (Windows) or Photoshop > Preferences > Cursors > Painting Cursors (Mac OS). Normal Brush Tip displays the standard Quick Selection cursor with a plus or minus sign to show the selection mode.
     

 Selecting with the Magic Wand Tool


The Magic Wand tool lets you select a consistently colored area (for example, a red flower) without having to trace its outline. You specify the color range, or tolerance, for the Magic Wand tool’s selection, based on similarity to the pixel you click.

You cannot use the Magic Wand tool on an image in Bitmap mode or on 32‑bits-per-channel images.
1. Select the Magic Wand tool .
2. Specify one of the selection options in the options bar. The Magic Wand tool’s pointer changes depending on which option is selected. (See diagram above.)
3. In the options bar, specify any of the following:

   Tolerance

   Determines the similarity or difference of the pixels selected. Enter a value in pixels, ranging from 0 to 255. A low value selects the few colors very similar to the pixel you click. A higher value selects a broader range of colors.

   Anti-aliased

   Creates a smoother-edged selection.

   Contiguous

   Selects only adjacent areas using the same colors. Otherwise, all pixels in the entire image using the same colors are selected.

   Sample All Layers

   Selects colors using data from all the visible layers. Otherwise, the Magic Wand tool selects colors from the active layer only.

4. In the image, click the color you want to select. If Contiguous is selected, all adjacent pixels within the tolerance range are selected. Otherwise, all pixels in the tolerance range are selected.

Optional: After you make any selection, click Refine Edge in the Control Panel to further adjust the selection boundary or view the selection against different backgrounds or as a mask. See Refine selection edges.

— From http://helpx.adobe.com/content/help/en/photoshop/using/making-selections.html