Comparison

Inkscape centerline trace vs VecSnap.

Inkscape's Centerline tracing is free and draws single lines. We ran it and VecSnap on the same three small JPGs and set the files side by side, every line at the same width.

  • Inkscape's own threshold, nothing tuned
  • Straight lines, curves, and where each one wins
A small black line drawing of a house front with a door and two windows, on white paper, up close, as Inkscape's centerline drew itInkscape
A small black line drawing of a house front with a door and two windows, on white paper, up close, as VecSnap's single lines drew itVecSnap
120 test images, every line scored
Inkscape centerlineAutoTrace 0.40.0 · free
70%of lines found
1.56stray ends
VecSnapSingle lines
99%of lines found
0.24stray ends

Inkscape centerline trace is the Centerline tracing mode of Trace Bitmap: free, on your computer, built on AutoTrace. It draws one open line down each stroke. On a large, clean drawing it does the job. On a small or compressed JPG it rounds corners and bends straight lines, where VecSnap's single lines stay straight; on curves the two are close. On 120 test images it found 70% of the lines, VecSnap 99%.

Updated 4 sources ↓

Side by side

How good is Inkscape's centerline trace?

Good on curves and clean drawings, weaker on straight lines in a small file: it rounds a square corner and bends a straight wall. We picked three drawings and gave both tools the same small JPG of each.

The teapot is the fair row: on curves the two are close. On the engine's bench of 120 test images, kept apart from all tuning, Inkscape's found 70% of the lines and left 1.56 stray ends an image; VecSnap found 99% and left 0.24.

A small black line drawing of a house front with a door and two windows, on white paperJPG
A small black line drawing of a house front with a door and two windows, on white paper, as Inkscape's centerline drew itInkscape
A small black line drawing of a house front with a door and two windows, on white paper, as VecSnap's single lines drew itVecSnap
A small black line drawing of a slatted garden gate with a diagonal brace, on white paperJPG
A small black line drawing of a slatted garden gate with a diagonal brace, on white paper, as Inkscape's centerline drew itInkscape
A small black line drawing of a slatted garden gate with a diagonal brace, on white paper, as VecSnap's single lines drew itVecSnap
A small black line drawing of a round teapot with a spout and a handle, on white paperJPG
A small black line drawing of a round teapot with a spout and a handle, on white paper, as Inkscape's centerline drew itInkscape
A small black line drawing of a round teapot with a spout and a handle, on white paper, as VecSnap's single lines drew itVecSnap

In Inkscape

How do I do a centerline trace in Inkscape?

Select the image, open Path, then Trace Bitmap, and choose Centerline tracing under Single scan. It needs Inkscape 1.0 or later.
  1. Import the image and click it, so it is selected.
  2. Open Path, then Trace Bitmap.
  3. On the Single scan tab, set Detection mode to Centerline tracing (autotrace).
  4. Click Apply. The trace lands on top of the image, so drag it aside to see it.

When it fails

Why is Inkscape's centerline trace not working?

Three causes come up most: the mode sits on the other tab, the preview does not show it, or a large image crashes it on Windows.
  • The option is missingLook under Single scan
    • Multiple scans has no centerline mode
    • It arrived with Inkscape 1.0, so update an older copy
  • Nothing showsPress Apply
    • The preview can miss this mode
    • The result is a thin stroke, easy to lose on top of the image
  • It crashesTry a smaller image
    • A Windows report has it quitting on a 2,000 px image
    • The same report has 400 px working

Double lines

How do I turn double lines into a single line in Inkscape?

Trace the picture again with Centerline tracing. Brightness cutoff and Edge detection follow both edges of every line, so a pen or laser goes round each line instead of along it.

If you only have the outlined vector, export it as a PNG first, then trace that.

The right tool

When should I use Inkscape instead of VecSnap?

Use Inkscape when the drawing is large and clean, when it must stay on your computer, or when you want to edit the lines yourself straight away. Use VecSnap when the file is small or compressed, or when straight lines must stay straight.
  • InkscapeFree, on your computer
    • Costs nothing, runs offline
    • Good on large, clean drawings
    • Edit the lines in the same app
  • VecSnapA small or rough file
    • Corners stay square on a small JPG
    • See the pen path before you pay
    • Pen, laser, PDF, EPS and DXF files

Try it

What does VecSnap make of my own drawing?

Drop it here. VecSnap draws it as single lines, and converting and previewing are free.

Drop your drawing. Get its SVG.

  1. Drop a line drawing, handwriting or a small JPG.
  2. Read the pen path it would draw.
  3. Keep the file for one credit, or leave it.

Method

How were the two tools compared?

The same file went to both tools, Inkscape's at its default brightness threshold, and every file is shown at the same line width.
  1. The input: the JPG in the first column, saved at 512 px and low quality on purpose.
  2. Inkscape's column: AutoTrace 0.40.0, the tool behind Centerline tracing, on the picture made black and white at 0.45, as Trace Bitmap does.
  3. VecSnap's column: the single lines a customer downloads for a pen or a laser.
  4. We picked these drawings, so they show where the two part. The bench's 120 images are the wider read: lines found against each drawing's own lines, and stray ends counted an image.

Questions

Inkscape centerline, answered.

Sources

Yes. Inkscape is free and open source, it runs on your computer, and your drawing never leaves it.

Where next

Keep going

Single line SVG converter

One line down the middle of each stroke, for a pen, foil or a laser.

Single lines

How to make an SVG for laser cutting

Why a traced SVG engraves some areas twice, and the file each laser app wants.

Guide · 5 min read

potrace vs VTracer vs VecSnap, measured

potrace and VTracer against VecSnap on the same images, every file counted.

Comparison · measured

Drop a drawing. Check the file.

Converting is free. You see the whole result before you spend anything.