Technique for finding the centerline of a curved object?


I'm curious to know if anyone knows of any effective techniques for finding the center line of a curved object.

In the screenshot below you'll see a crude version of what I mean.

Shape with a drawn centerline path

Is there any way to get that line to perfectly trace the center, or is it easiest to just eyeball it?

Photoshop or Illustrator techniques are acceptable.

3/30/2016 12:39:00 AM

Accepted Answer

If you are happy with just getting close, this works in Illustrator - especially for an image that has a consistent width like your example.

  1. Draw a circle that is the same width as your object's width

  2. Copy/paste the circle as many times as needed and distribute around the object. Use enough of them to follow the shape fairly closely

  3. Using the pen tool simply draw a line through the centerpoints of the circles you made. Just connect them straight, don't worry about curves.

  4. Use the smooth tool to curve the line you just made. (just follow the curve of the original with the smooth tool) If necessary you can make curve adjustments separately at the bezier points.

  5. Delete the circles

The picture below will demonstrate a little better.

Find the middle line

4/9/2016 3:27:00 PM

Use Illustrator's Blend

  1. Outline your type (Type → Create Outlines)

  2. If needed, ungroup the paths and/or release the compound path (Object → Ungroup / Object → Compound Path → Release)

  3. Use the Direct Selection Tool (A) to select the end paths and delete those segments. You should now have 2 separate paths.

  4. Set the blend options to 1 step (Object → Blend → Blend Options)

  5. Create your blend (Object → Blend → Make)

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Blend will usually give the desired result but can sometimes fail with more complex curves.

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If the blend fails, use the Scissors Tool (C) to cut both paths at the problem areas and recreate the blend for each section.

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For more complex letters or shapes, divide the shape in to more manageable sections. Then create a blend for each section.

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