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2.5.  Fuzzy Selection Tool (Magic Wand)

Revision History
Revision $Revision: 1.49 $ 2006-06-05 j.h

Figure 8.10.  Magic Wand tool icon in the Toolbox

Magic Wand tool icon in the Toolbox

The Fuzzy Select (Magic Wand) tool is designed to select areas of the current layer or image based on color similarity. It starts selecting when you click at a spot in the image, and expands outward like water flooding low-lying areas, selecting contiguous pixels whose colors are similar to the starting pixel. You can control the threshold of similarity by dragging the mouse downward or to the right: the farther you drag it, the larger the selected region. And you can reduce the selection by dragging upwards or to the left.

When using this tool, it is very important to pick the right starting point. If you select the wrong spot, you might get something very different from what you want, or even the opposite.

The Wand is a good tool for selecting objects with sharp edges. It is fun to use, so beginners often start out using it a lot. You will probably find, however, that the more you use it, the more frustrated you become with the difficulty of selecting exactly what you what, no more, no less. Perhaps the most frustrating aspect is that after you have released the mouse button, you can't make small adjustments to the threshold: you have to start over again from scratch. More experienced users find that the Path and Color Select tools are often more efficient, and use the Wand less. Still, it is useful for selecting an area within a contour, or touching up imperfect selections. It often works very well for selecting a solid-colored (or nearly solid-colored) background area.

Note that as the selected area expands outward from the center, it does not only propagate to pixels that touch each other: it is capable of jumping over small gaps. The distance it can jump over is set in the Tool Options page of the Preferences dialog: the "Default threshold" for Finding Continguous Regions. By raising or lowering this value, you can make the Magic Wand either more or less aggressive. (Filling with the Bucket Fill and Blend tools will also be affected.)

2.5.1.  How to Activate

The Magic Wand Tool can be activated from an image menu as Tools->Selection Tools->Fuzzy Select; from the Toolbox by clicking on the tool icon ; or from the keyboard using the shortcut z. ("Z" stands for "Zauber", the German word for Magic.)

2.5.2.  Key modifiers (Defaults)

The Fuzzy Select tool does not have any special key modifiers, only the ones that affect all selection tools in the same way. See Selection Tools for help with these.

2.5.3.  Options

Figure 8.11.  Tool Options for the Magic Wand tool

Tool Options for the Magic Wand tool
[Note] Note

See Selection Tools for help with options that are common to all these tools. Only options that are specific to the Magic Wand tool are explained here.

Finding Similar Colors

These options affect the way the Magic Wand expands the selection out from the initial point.

Select Transparent Areas

This option gives the Magic Wand the ability to select areas that are completely transparent. If this option is not checked, transparent areas will never be included in the selection.

Sample Merged

This option becomes relevant when you have several layers in your image, and the active layer is either semi-transparent or is set to another Layer Mode than Normal. If this is the case, the colors present in the layer will be different from the colors in the composite image. If the "Sample Merged" option is unchecked, the wand will only react to the color in the active layer when it creates a selection. If it is checked it will react to the composite color of all visible layers. For further information, see the glossary entry Sample Merged.

Threshold

This slider determines the range of colors that will be selected at the moment you click the pointer on the initial point, before dragging it: the higher the threshold, the larger the resulting selection. After the first button-press, dragging the pointer downward or to the right will increase the size of the selection; dragging upward or to the left will decrease it. Thus, you have the same set of possibilities regardless of the Threshold setting: what differs is the amount of dragging you have to do to get the result you want.


 
 
  Published under the terms of the GNU General Public License Design by Interspire