2.3. Ellipse Selection

2.3. Ellipse Selection
	2. Selection Tools

图 14.14. Ellipse Select icon in the Toolbox

The Ellipse Selection tool is designed to select circular and elliptical regions from an image, with high-quality anti-aliasing if you want it. For information on selections and how they are used in GIMP see Selections; for information on features common to all selection tools see Selection Tools.

This tool is also used for rendering a circle or ellipse on an image. To render a filled ellipse, create an elliptical selection, and then fill it using the Bucket Fill tool. To create an elliptical outline, the simplest and most flexible approach is to create an elliptical selection and then stroke it. However, the quality of anti-aliasing with this approach is rather crude. A higher quality outline can be obtained by creating two elliptical selections with different sizes, subtracting the inner one from the outer one; however this is not always easy to get right. The command Select → Border... makes it easy.

2.3.1. Activating the tool

You can access the Ellipse Selection Tool in different ways:

From the image menu bar Tools → Selection Tools → Ellipse Select;
By clicking on the tool icon in the ToolBox,
By using the keyboard shortcut E.

2.3.2. Key modifiers

	注意
	See Selection Tools for help with modifier keys that affect all these tools in the same way. Only effects options that are specific to this tool are explained here.

Ctrl: Pressing the key after starting your selection, and holding it down until you are finished, causes your starting point to be used as the center of the selected ellipse, instead of a corner of the rectangle that may contain it. Note that if you press the Ctrl key before starting to make the selection, the resulting selection will be subtracted from the existing selection.
滑移: Pressing the Shift key after starting your selection, and holding it down until you are finished, constrains the selection to be a circle. Note that if you press the Shift key before starting to make the selection, the resulting selection will be added to the existing selection.
Ctrl+滑移: Pressing both keys combines the two effects, giving you a circular selection centered on your starting point.

2.3.3. Tool handling

图 14.15. Example of Ellipse Selection.

When this tool is selected the mouse pointer comes with a circle icon as soon as it is over the image. A drag-and-drop allows you to get an ellipse (or a circle) within a rectangular box. When the mouse button is relaxed, a dotted line (“marching ants”) outlines the elliptic selection. It's not necessary to adjust the selection with care; you can resize it easily later.

When the pointer is moving on the canvas, the pointer and selection aspects change. You can change the size of the selection by using handles. See Tool handling within the rectangular chapter.

2.3.4. 选项

图 14.16. Tool Options for the Ellipse Select tool

Normally, tool options are displayed in a window attached under the Toolbox as soon as you activate a tool. If they are not, you can access them from the image menu bar through Windows → Dockable Windows → Tool Options which opens the option window of the selected tool.

	注意
	See Selection Tools Options for help with options that are common to all these tools. Only options that are specific to this tool are explained here.

Modes; Antialiasing; Feather edges: Common select options.
All other options: All these options work exactly the same way, they were described for the rectangular selection already. See for 第 2.2.4 节 “工具选项” details.