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2.7. Scissors Tool

Revision History
Revision $Revision: 1.43 $ 2006-06-05 j.h

Figure 8.14.  Intelligent Scissors tool icon in the Toolbox.

Intelligent Scissors tool icon in the Toolbox.

The Intelligent Scissors tool is an interesting piece of equipment: it has some features in common with the Lasso, some features in common with the Path tool, and some features all its own. It is useful when you are trying to select a region defined by strong color-changes at the edges. To use the Scissors, you click to create a set of "control nodes" at the edges of the region you are trying to select. The tool produces a continuous curve passing through these control nodes, following any high-contrast edges it can find. If you are lucky, the path that the tool finds will correspond to the contour you are trying to select.

Each time you left-click with the mouse, you create a new control point, which is connected to the last control point by a curve that tries to follow edges in the image. To finish, click on the first point (the cursor changes to indicate when you are in the right spot). You can adjust the curve by dragging the control nodes, or by clicking to create new control nodes. When you are satisfied, click anywhere inside the curve to convert it into a selection.

[Warning] Warning

Be sure not to click inside the curve until you are completely done adjusting it. Once you have converted it into a selection, undoing takes you back to zero, and you will have to to start constructing the curve again from scratch if you need to change it. Also be sure not to switch to a different tool, or again all of your carefully created control nodes will be lost. (But you still can transform your selection into a path and work it with the Path tool.)

Unfortunately, there seem to be some problems with the edge-following logic for this tool, with the result that the selections it creates tend to be pretty crude in a lot of cases. A good way to clean them up is to switch to QuickMask mode, and use paint tools to paint in the problematic parts. On the whole, most people find the Path tool to be more useful than the Scissors, because, even though it does not have the intelligent edge-finding capability, the paths it produces persist until you delete them, and can be altered at any time.

2.7.1. How to Activate

The Intelligent Scissors can be activated from an image menu as Tools->Selection Tools->Intelligent Scissors; from the Toolbox by clicking on the tool icon ; or from the keyboard using the shortcut i.

2.7.2. Key modifiers (Defaults)

The Scissor 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.

2.7.3. Options

Figure 8.15.  Tool Options for the Intelligent Scissors

Tool Options for the Intelligent Scissors
[Note] Note

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

Show Interactive Boundary

If this option is enabled, dragging a control node during placement will indicate the path that will be taken by the selection boundary. If it is not enabled, the node will be shown connected to the previous node by a straight line while you are dragging it around, and you won't see the resulting path until you release the pointer button. On slow systems, if your control nodes are far apart, this may give a bit of a speed-up.

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