4.2. パスの性質

Paths, like layers and channels, are components of an image. When an image is saved in GIMP's native XCF file format, any paths it has are saved with it. The list of paths in an image can be viewed and operated on using the Paths Dialog. You can move a path from one image to another by copying and pasting using the pop-up menu in the Paths dialog, or by dragging an icon from the Paths dialog into the destination image window.

GIMP のパスは数学でいうところのベジエ曲線に属しています。 その語句の実践的な意味は、 この曲線が アンカーハンドル で定義されるということです。 アンカーはパスが通る点です。 ハンドルはアンカー点に入って抜けるそれぞれのパスの方向を定めます。 アンカーひとつにつき 2 つのハンドルがついています。

Paths can be very complex. If you create them by hand using the Paths tool, they probably won't contain more than a few dozen anchor points and usually a less than that. However, if you create them by transforming a selection into a path, or by transforming text into a path, the result can easily contain hundreds or even thousands of anchor points.

パスには数本の 成分 が入れられます。 成分は一本のパスとそれに貫かれたたくさんのアンカー点からなります。 数本の成分をまとめてパスに含められることによって、 それを選択に変換したときに飛び地のある選択が作れます。

パスの成分はそれぞれ 開いた ものか 閉じた もののいずれかです。 閉じた成分は終点のアンカーが始点のアンカーに繋っています。 パスを選択に変換するときには、 開いた成分はいずれも終点から始点まで自動的に直線で結ばれ閉じられてから変換されます。

Path segments can be either straight or curved. A path is called polygonal if all of its segments are straight. A new path segment is always created straight; the handles for the anchor points are directly on top of the anchor points, yielding handles of zero length, which produces straight-line segments. Drag a handle away from an anchor point to cause a segment to curve.

One nice thing about paths is that they use very few resources, especially in comparison with images. Representing a path in RAM requires storing only the coordinates of its anchors and handles. Therefore, it is possible to have literally hundreds of paths in an image without causing any significant stress to your system. Even a path with thousands of segments consumes minimal resources in comparison to a typical layer or channel.

Paths can be created and manipulated using the Paths tool.