Centerline Trace

One stroke per line, instead of two outlines

Every tracer you have probably tried, including our own Color and B&W modes, is an outline tracer. It finds the edges of the dark areas and turns each one into a filled shape. That is exactly right for a logo or a sticker. It is wrong for a drawing that is meant to be drawn, because a line in your sketch comes out as a long, thin shape with two edges. Send that file to a laser on a line or score setting and it runs down one side of every line and back up the other. A pen plotter draws each line twice, slightly apart. A Cricut pen does the same, and the result looks doubled and heavy.

Centerline tracing finds the middle of each line instead and gives you a single stroke that follows it. We measured the difference on the sample drawings above. For the kitten, the outline trace adds up to 2.3 times as much path as the centerline trace. For the signature it is 3 times as much. That is how much extra travel, time and scorching an outline file asks of your machine, and every bit of it is spent going over lines twice.

Job	Outline trace gives you	Centerline trace gives you
Laser scoring or line engraving	Every line scored twice, a hairline apart	One pass down each line
Pen plotter (AxiDraw and similar)	Doubled lines, twice the plotting time	One pen stroke per line
Cricut or Silhouette pen, score	Two parallel lines per stroke	A single drawn line
Vinyl cutting, stickers	The right result: shapes to weed	Not what you want: use Color or B&W
Embroidery running stitch	Outlines to stitch around	A path to stitch along
Editing the drawing	Thick shapes to reshape	Clean strokes to restyle, thicken or recolor

How to convert a drawing to a single-line SVG

1. Add your drawing. Drop a scan, a phone photo or a PNG onto the tool above. It is read in your browser. Nothing is uploaded.
2. Check the strokes. Centerline mode is already selected on this page. Zoom in, or turn on Outlines to see each stroke as the thin line a laser follows: each line should be one stroke, with no little side branches.
3. Clean up if needed. Open Advanced. Despeckle drops dust, paper grain and tiny marks; raise it for a noisy scan. Smoothing controls the curves: higher gives flowing lines, lower keeps sharp corners on lettering and technical drawings.
4. Download the SVG. The file has one path per stroke, with no fill, ready for LightBurn, Glowforge, xTool, Cricut Design Space, Silhouette Studio, Inkscape or plotter software.

What traces well, and what doesn't

Centerline tracing is built for drawings made of lines. The closer your image is to that, the cleaner the strokes:

Image	Result	Verdict
Line drawing, coloring page, comic inks	One stroke per line, joined through crossings	✅ Ideal
Signature or handwriting	A handful of smooth strokes	✅ Ideal
Doodle with colored fills	The dark lines are traced; the colored fills are ignored	✅ Good
White lines on a dark background	Detected automatically and traced the same way	✅ Good
Pencil sketch with shading	Outlines trace well; hatching becomes many short strokes	⚠️ Mixed
Very fine lines in a large scan	Lines thinner than about a pixel at 1,600 px can break up	⚠️ Mixed
Filled shapes, silhouettes, bold logos	Reduced to a skeleton that rarely looks like the shape	❌ Use Color or B&W
Photographs	A tangle of strokes	❌ Not a line drawing

Using the file on your machine

• LightBurn. Import the SVG and put the strokes on a Line layer to score or cut along them. Because each line is a single path, the job time drops and nothing gets burned twice.
• Glowforge. Upload the SVG and set the strokes to Score. Score follows the line once, which is the look you drew.
• xTool Creative Space. Import the SVG and give the strokes a score or line processing type rather than fill.
• Cricut Design Space. Upload the SVG, select the strokes and change their operation to Pen or Score. Attach them so the drawing stays in position.
• Pen plotters. Open the SVG in Inkscape and plot it with your plotter's extension (for an AxiDraw, the AxiDraw extension). Each stroke is plotted once.
• Embroidery. Import the strokes into your digitizing software as running-stitch paths.

Stroke width in the file is only for how it looks on screen. Machines follow the path, so the line you get depends on the pen, the laser power and speed, or the stroke width you set in your design software.

How centerline tracing works

Under the hood the tool runs a short pipeline, entirely in your browser:

1. Ink and paper. It splits the image into ink and paper by brightness. The side that owns the image border is paper, so light lines on a dark background work too. If the ink side is mostly a second, lighter tone, that tone is treated as colored fill and left out.
2. Cleanup. Specks smaller than the Despeckle size are removed, and pinholes inside thick lines are filled, so they don't turn into tiny loops.
3. Thinning. The ink is peeled away one pixel layer at a time until only a one-pixel skeleton down the middle of each line is left (the Zhang-Suen method).
4. Spur pruning. Thinning grows short side branches at line ends and bumps. Any branch shorter than the line is wide is cut off.
5. Joining. Where lines cross, branches that continue straight through are joined, so an X becomes two strokes rather than four stubs.
6. Curve fitting. Each stroke is simplified and fitted with smooth curves, keeping sharp turns as corners. The width of each stroke is measured from your drawing.

Getting a clean result

• Start dark and flat. A dark pen on white paper traces far better than pencil. If you photograph a drawing, do it in even daylight and crop close to the lines.
• Scan, don't squint. A 300 dpi scan beats a phone photo, and a large image beats a thumbnail: thin lines need enough pixels to survive.
• Remove what isn't a line. Erase shading, text notes and ruler marks before tracing, or delete their strokes afterward in your design software.
• Raise Despeckle for scans with dust or paper texture. Lower it if small dots, like the dot on an i, disappear.
• Tune Smoothing to the drawing. Handwriting and organic shapes look best around 1.5 to 2.5. Lettering, floor plans and technical drawings keep crisper corners at 0.5 or below.

Centerline tracing elsewhere

Centerline tracing is harder to find than it should be. Inkscape can do it through a separately installed extension. Illustrator's Image Trace can create strokes instead of fills for lines up to a set width. LightBurn added its own center line trace in its 2.2 early-access release in September 2026, which helps LightBurn owners but nobody else. Most online converters only trace outlines. This page gives you centerline strokes in the browser, free, without an upload or an install, for any machine that reads SVG.