A clipping path is a graphical selection tool used in image editing software. It is a vector element, meaning that it is mathematically defined and not dependent on the resolution of any graphic being edited. The most common use of a clipping path is to nondestructively change the appearance of certain portions of a document. In other words, with the use of a clipping path, specific parts of an image can be hidden, made transparent or otherwise made to look different without actually modifying those pixels.
Depending on the software package being used, the creation of a clipping path can be accomplished by several methods. The typically preferred method is through input of points one at a time, because it tends to be the most precise. The path is constructed as a closed shape and can usually contain as many points as desired. The time to perform any operation using the path, however, is longer as the number of path points is increased. The software, however, usually performs transitions between each of the points to minimize how many are needed, particularly along curves.
A clipping path is most often utilized as a sharp-edged selection; in other words, pixels are wholly part of the selection or not part of it. As a result, jagged edges can occur as a selection moves around individual pixels. Depending on what program is being used, though, anti-aliasing can be applied to reduce or eliminate the roughness. In this instance, some of the affected pixels are only partially selected or transparent, and the end result is a much smoother line in the instance of a path that cuts across pixels.
Once created, a clipping path can be employed in several ways. The pixels inside or outside of it can be copied to memory and used in another application. They also can be part of a new picture or image layer in the program that created the path. The clipping path also can be used to select what parts of an image appear transparent and by what percent.
The key advantage of a clipping path — and the reason it is most likely to be used — is its flexibility. Most image editors have basic selection tools, but a clipping path has several key differences compared to those tools. First, it is very easily editable. Second, with most image editors, the path can be saved and subsequently recalled for later use. Most importantly, a clipping path also can dynamically modify the appearance of an image yet provide the ability to quickly undo those edits.