Can you turn an outline back into a stroke in Adobe Illustrator?

If you’ve ever received expanded, outlined, traced, or stock vector artwork in Adobe Illustrator, you may have run into a frustrating problem: you have the outline of a shape, but what you really need is the single path running through its center.

Finding that centerline, or center path, can be useful when you want to turn outlined artwork back into something closer to an editable stroke, simplify vector artwork, or work with paths for processes such as engraving, cutting, or technical production.

Illustrator doesn’t have a simple “find centerline” command, and recreating the original path manually can be time-consuming. For simple shapes, however, the Path Zipper Tool, part of the VectorScribe plugin from Astute Graphics, offers another approach.

How to find a centerline in Illustrator

1. Find the Path Zipper Tool

Open Illustrator’s Advanced toolbar and find the Path Zipper Tool stacked under the PathScribe Tool.

2. Prepare closed or outlined shapes

To create a centerline, you first need two open paths that represent either side of the line you want to create. Path Zipper has convenience functions that make it easier to prepare existing outlined artwork.

Hover over a closed path and hold Alt or Option to cut the anchor points that fall within the Path Zipper Tool’s circular cursor. This lets you quickly split a closed shape into open paths without switching tools.

You can also use the convenience functions to delete a path segment within the circle. This is useful with outlined letters and other shapes where you need to remove parts of the outline before creating your centerline.

Astute Buddy displays the available keypresses while you work, making it easier to see which Path Zipper functions are available.

3. Bring the endpoints together

Once you have the two open paths you need, use Path Zipper to make their corresponding start points coincident, then repeat the process with the end points.

4. Zip the two paths together

Zip the two sides together and Path Zipper averages their positions, bringing them together to create a path through the center.

By default, when the resulting paths lie directly on top of each other, one is deleted. A yellow annotation lets you know this has happened. You can change this behavior in the Path Zipper preferences if you want to retain both paths.

What about more complex shapes?

The same process can be used on simple outlined letters and other expanded artwork. Cut the paths where needed, delete unwanted segments, bring the corresponding start and end points together, then zip the paths to find the centerline.

The technique works best with simple geometry. Shapes containing loops or more complicated compound paths can require additional work because the software cannot always determine the intended direction of the centerline.

For simpler artwork, Path Zipper provides a quick way to turn two sides of an outlined shape into a useful center path without manually redrawing it.