5.2. Свойства контура

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 paths belong to a mathematical type called «Bezier paths». What this means in practical terms is that they are defined by anchors and handles. «Anchors» are points the path goes through. «Handles» define the direction of a path when it enters or leaves an anchor point: each anchor point has two handles attached to it.

Сегменты контура могуть быть прямыми или изогнутыми. Контур, целиком состоящий из прямых называется "многоугольным". Когда вы создаёте сегмент контура, он создаётся прямым, поскольку рычаги управляющей точки размещаются на прямо управляющей точке, с нулевой длиной, что и создаёт сегмент - прямую линию.

Одна приятная вещь в контурах это то, что они очень лёкгие в плане потребления памяти, особенно в сравнении с изображениями. Контур требует памяти только для хранения координат управляющих и рычагов: 1К памяти достаточно для размещения весьма сложного контура, но не достаточно для размещения RGB слоя даже размером 20x20 пикселей. Поэтому можно содержать буквально сотни контуров в изображении без каких-либо стрессовых нагрузок для вашей системы.

Each component of a path can be either open or closed: «closed» means that the last anchor point is connected to the first anchor point. If you transform a path into a selection, any open components are automatically converted into closed components by connecting the last anchor point to the first anchor point with a straight line.

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 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: 1K of memory is enough to hold a complex path, but not enough to hold a small 20x20 pixel RGB layer. Therefore, it is possible to have literally hundreds of paths in an image without causing any significant stress to your system; the amount of stress that hundreds of paths might cause you, however, is another question. 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 Path tool.