Selections and Extractions
The first task you do with image manipulation is usually to select a portion or portions of the image for making changes or to extract some part of the image to be trasferred onto a different one.
Photoshop has a variety of selection tools that can be use for the above purposes, plus an extract command.
Marquee Tool:
The most basic of all the selection tools is the Marquee Tool. This is located at the top left corner of the toolbox. You can utilize it by clicking the Marquee Tool icon or by hitting the M key.
When you click on the small black triangle at the bottom right corner of the Marquee Tool, more optional tools willemerge, such as the Elliptical Marquee Tool used for creating circular or oval selections.
Addi-tional settings are also available in the Options Bar such as the Feather setting
To make a selection with the Marquee Tool, just drag across the portion of the image you want to select while holding down the mouse button. Once you release the mouse button, your selection will be surrounded by flickering
dashed lines. To create a selection that is perfectly square or round, hold down the Shift key as you drag around the area you want to select. To create a selection that extends outward from its center, hold down the Alt key as you drag.
Lasso Tool:
Now we consider the Lasso Tool. It is used for making irregular selections because the boundary will follow your curser as it is dragged around on the canvass.
To access it, click on the Lasso Tool icon in the toolbox or hit the L key. Clicking on the small black triangle at the bottom right corner of the Lasso Tool icon will show the Polygon Lasso and
Magnetic Lasso Tool.
With the Lasso Tool, you can trace around the portion of the image you want to select to create a free-hand selection border.
By holding down the Alt key (Windows), instead of dragging, you can click around distinct points of the area you want to select.
This is preferable if the outline is not constantly changing direction. Undesirable for use with minute details.
The Polygon Lasso is used to make straight-edge selections. Click once where you want the selection to begin; move your cursor to the next selection point and click again;
and continue in this fashion until you have enclosed the portion of the image you want to select within the selection border. Anti-aliasing and Feathering options are
available in the Options Bar for both the regular Lasso Tool and the Polygon Lasso Tool.
The Magnetic Lasso Tool works much like the regular Lasso Tool except that as you trace around the portion of the image you want to select,
the Magnetic Lasso creates a selection border than snaps to the edge of a defined area of your image. To use the MAGNETIC LASSO, click once on the portion of
your image that you want to select to set a starting point, and then trace around the portion of the image that you want to select.
Notice that after the initial click, you don’t have to hold down the mouse button. As you trace, the selection border snaps to the edge of your selection,
dropping fastening points along the way. You can add more fastening points by clicking as you trace.
There are special settings in the Magnetic Lasso Options Bar for Width, Frequency and Edge Contrast. Width is the distance, in pixels, from the edge of
your selection to the cursor that the Magnetic Lasso can detect as you trace around the image. The smaller the value you specify,
the more precise edge detection will be, and vice versa. If the portion of the image you want to select has lots of grooves and
jags, use a small value like 1 pixel. Frequency is the rate at which the Magnetic Lasso will place fastening points as you trace around the image.
In general, use low values for smooth edges and high values for edges with lots of nooks and crannies. Edge Contrast works by detecting
contrast between the edge of the portion of the image you want to select and its background area. Use high Edge Contrast for edges that contrast sharply with
the background and low Edge Contrast values for poorly contrasted edges.
Magic Wand Tool
The Magic Wand Tool is used to select portions of an image that are of the same color range.
In the Options Bar, you can set a Tolerance for your selection at any value between 0 and 255. With a high Tolerance setting, more gradations of colour within that particular colour range
will be selected, resulting in a larger area on the image. To keep the selection tight, use a small Tolerance value such as 20. For a single colour tone, use a value of 1.
If you want to select more than one portion of an image, just hold down the Shift key as you click with the Magic Wand Tool on the next portion of the image you want to select.
You can access the Magic Wand Tool by clicking on its icon in the tool-box or by hitting the W key.
The Select Menu
You should also familiarize yourself with the various commands on the Select drop-down menu. The moist handy of these are: Select All; Deselect; Inverse; Hide Edges; Modify.
With the Modify command there are also sub-commands to Grow, Similar, Expand and Contract your selection. The Grow sub-command enlarges the selection based upon the Tolerance value set for the Magic Wand Tool.
Each application increases the Tolerance value of the selection by two. The Similar sub-command will include every instance of the same color range picked by the Magic Wand Tool throughout the entire image.
To add to a selection, hold down the Shift key and make another selection. To subtract from a selection, hold down the Alt key and drag around the area in the selection you want to deselect.
Extractions
To make extractions from an image, you basically select the area you want and Copy it. Then Paste it into another image or a new image.
In addition to the selection tools above, Photoshop also includes an Extract command in the Image drop-down menu which allows you to isolate an object from its background and erase the background to transparency.
To extract an object, you use tools in the Extract dialog box. First you draw a highlight that marks the edges of the object, and define the object's interior. Then you can preview the extraction and redo it or touch up the result as needed.
When you extract the object, Photoshop erases its background to transparency. Pixels on the edge of the object lose their color components derived from the background, so they can blend with a new background without producing a color halo.
To avoid losing the original image information, duplicate the layer or make a snapshot of the original image state.
If you are highlighting a well-defined edge, select Smart Highlighting. This option helps you keep the highlight on the edge, and applies a highlight that is just wide enough to cover the edge, regardless of the current brush size.
Smart Highlighting can greatly improve the extraction when the object and background have similar colors or have textures. If the object is especially intricate or lacks a clear interior, make sure that the highlight covers the entire object,
and then select Force Foreground. To specify the amount of smoothing of the extracted object, drag the Smooth slider or enter a value. It is usually best to begin with a zero or small value to avoid unwanted blurring of details. If there are sharp artifacts in the extraction result, you can increase the Smooth value to help remove them in the next extraction.
Click OK to apply the final extraction. On the layer, all pixels outside the extracted object are erased to transparency.
Quick Mask
You can also make sophisticated selections and extractions using Quick Mask. In the Photoshop tool bar click on the Quick Mask Mode icon at the bottom right (circle within a square). Make sure the Selected Areas option is active (dark circle within white square).
This allow you to use any paintbrush configuration to paint over the areas of the image you wish to select. For instance, you can use a soft brush to achieve soft edges with a Feathering effect, or use a solid brush for crisp edges. For thin lines you can set the brush size to 1 or 2 pixels.
This is the best way to capture intricate details and make selections that contain small hollow areas.
After your masked the area you want on the image, exit Quick Mask Mode by clicking on the Standard Mode icon to the left. You are left with a resulting dashed outline surrounding the selected area. Copy this and Paste it as a layer or onto another image. You can also open a New File and Paste it as a new image.
This is the best methos for making detailed selections because of the numerous options available to the Paint Brush.
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