User Guide

GNU Image Manipulation Program
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Figure 7.9: Appearance of a path while it is being manipulated using the Path tool.
Black squares are anchor points, the open circle is the selected anchor, and the two open squares are its handles. Note that this
path has two components.
Paths can be created and manipulated using the Path tool. 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 along with it. The list of paths in an image can be
viewed and operated on using the Paths dialog. If you want to move a path from one image to another, you can do so by copying
and pasting using the popup menu in the Paths dialog, or by dragging an icon from the Paths dialog into the destination image’s
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.
Paths can be very complex. If you create them by hand using the Path tool, unless you are obsessive they probably won’t contain
more than a few dozen anchor points (often many fewer); but if you create them by transforming a selection into a path, or by
transforming text into a path, the result can easily contain hundreds of anchor points, or even thousands.
A path may contain multiple components. A ‘component’ is a part of a path whose anchor points are all connected to each other
by path segments. The ability to have multiple components in paths allows you to convert them into selections having multiple
disconnected parts.
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 all of whose segments are straight is called ‘polygonal’. When you create
a path segment, it starts out straight, because the handles for the anchor points are initially placed directly on top of the anchor
points, yielding handles of zero length, which produce straight-line segments. You can make a segment curved by dragging a
handle away from one of the anchor points.
One nice thing about paths is that they are very light in terms of resource consumption, especially in comparison with images.
Representing a path in RAM only requires storing the coordinates of its anchors and handles: 1K of memory is enough to hold
quite a complex path, but not enough to hold even a 20x20 pixel RGB layer. Therefore, it is quite possible to have literally
hundreds of paths in an image without putting any significant stress of your system. (How much stress managing them would
put on you is, of course, another question.) Even a path with thousands of segments consumes minimal resources in comparison
to a typical layer or channel.
7.5.2 Paths and Selections
GIMP lets you transform the selection for an image into a path; it also lets you transform paths into selections. For information
about the selection and how it works, see the Selection section.
When you transform a selection into a path, the path closely follows the ‘marching ants’. Now, the selection is a two-dimensional
entity, but a path is a one-dimensional entity, so there is no way to transform the selection into a path without losing information.
In fact, any information about partially selected areas (i.e., feathering) will be lost when the selection is turned into a path. If the