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Centerline tracing: single-line SVG and DXF (Beta)

Trace drawings and lettering along the middle of each stroke: one line per stroke for engravers, plotters and CNC.

Opens: PNG, JPEG, WebP, GIF, HEIC, AVIF, BMP, TIFF, ZIP
Saves: SVG, PDF, EPS, DXF, ZIP

Vectorize

Pictures
Choose files… or drop them here
.png, .jpg, .jpeg, .jfif, .webp, .gif, .heic, .heif, .hif, .avif, .bmp, .tif, .tiff, .ico, .tga, .qoi, .pbm, .pgm, .ppm, .pnm, .apng, .zip · up to 200 MB each, 50 files max
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    One picture or many, or a .zip of a folder (sub-folders are kept in the result).

    Options
    Picture type

    Each picture shows a sample: the original on the left, its tracing on the right. The choice sets every setting below; anything you change is laid over it.

    Tracing method

    Usually left as the picture type sets. Single lines (red in the pictures) follow the middle of each stroke, for engraving, plotters and embroidery.

    Empty: decided from the picture. The background counts as a colour.

    The colour around the edge of the picture is not traced.

    Trace pixels that are

    Unlike the background: any colour that stands out. Darker than a level: dark marks only, so highlighter and faint pencil drop out. Darker than the surroundings: pages with shadows or uneven light. Not transparent: the shape of a cut-out picture. One colour: only marks of that colour.

    0 is black, 255 white. Pixels darker than this are traced: raise it for faint pencil.

    A hex colour, e.g. #e30613.

    More options

    Empty: as the picture type sets (12 for logos, 24 for clip art, 32 for photos, 64 for pixel art).

    Optional, for vinyl or thread colours: hex colours separated by commas, e.g. #000000, #ffffff, #e30613. Every area takes the nearest of them.

    Layering

    Cut-out shapes fit together like a puzzle, with holes where others sit: right for cutting and editing. Stacked shapes lie whole on top of each other: fewer nodes and no hairline gaps on screen.

    Colour difference: about 2 is barely visible, 12 a clear shade, 30 or more takes in neighbouring colours.

    How far around each pixel the light is measured. A little more than the thickest stroke works well.

    How much darker than its surroundings a pixel must be: lower picks up fainter marks (and more paper texture).

    Traces the other part: use it when the tracing shows the background instead of the drawing.

    Empty: the drawing's own colour. A hex colour such as #000000 makes them all that colour.

    Evens out rough pencil and paper texture. Empty: as the picture type sets (0 to 0.8).

    Width of the single lines. Empty or 0: measured from the picture.

    Empty or 0: decided from the line width.

    Thicker ink becomes filled shapes. Empty or 0: decided from the picture.

    Removes dust, noise and tiny holes. Empty: as the picture type sets (6 for logos, 20 for scans, 30 for photos).

    How far outlines may stray from the pixel edges: 0.3 follows them closely, 1.5 rounds them off. Empty: as the picture type sets.

    0 keeps every corner sharp, 1.34 rounds them all, about 1 looks natural. Empty: as the picture type sets.

    How far joined curves may stray: larger gives fewer nodes. Empty: as the picture type sets (0.25 to 0.5).

    Circles and ellipses

    The squares mark nodes: an exact circle needs only four.

    Against JPEG blocks, film grain and scanner dust; higher also rounds off small details. Empty: as the picture type sets.

    The unit of the drawing's width and height. DXF files are in millimetres unless centimetres or inches are chosen.

    In the size unit above, e.g. 100 for a 100 mm wide design. The height follows the picture's proportions. Empty: from the resolution below.

    Sets the physical size when no width is given: a 960 px wide picture at 96 is 10 inches (254 mm) wide, at 300 it is 3.2 inches.

    What cutters and lasers follow as cut lines. Single lines keep their width.

    Paints the background colour behind the shapes (SVG, PDF and EPS).

    Some viewers draw faint seams where colour shapes meet. A thin edge in each shape's own colour hides them.

    For checking the tracing against the picture in Inkscape or Illustrator. Makes the SVG larger.

    Your files are deleted after processing.

    Ordinary tracing goes around the edge of the ink: a pen stroke becomes a long thin shape with two edges. That is right for printing and vinyl, but wrong for an engraver, a pen plotter, a drag knife or single-line lettering, which should travel along each stroke once. Centerline tracing follows the middle of every stroke instead and gives one line per stroke, with a width.

    How to trace along the centre of the lines

    1. Upload a drawing, handwriting, a technical sketch or line art, ideally dark lines on light paper.
    2. Keep the picture type Single lines (centerline). For drawings that also have filled areas, choose Pencil or pen sketch: thin strokes become single lines and thick areas filled shapes.
    3. Download the SVG, and the DXF if your machine software prefers it. In the SVG every line is a stroke with round ends; in the DXF it is an open polyline (closed for loops such as an O).

    Settings that matter

    • Line width (More options): the width of the lines in the SVG. Left empty, it is measured from the strokes in your picture. It only changes how the lines look; a machine uses its own tool width.
    • Leave out lines shorter than: drops stray marks and dust. Left empty, it follows the line width.
    • Smooth the drawing before tracing: evens out rough pencil and paper texture, so lines don't wobble. Raise it a little for pencil, keep it low for fine pen.
    • Trace pixels that are: for faint pencil choose Darker than a brightness level and raise the level; for a photo of a page with shadows choose Darker than their surroundings.

    Where lines meet

    Strokes that run on through a crossing are joined into one line, so a cross is two lines rather than four. Check the preview at corners, junctions and line ends: the tracing follows the middle of the ink, so where strokes meet in a thick or blotchy join, the lines can come out slightly rounded or shortened.

    Good to know

    • Centerlines work for strokes of roughly even width. A big filled area has no single middle line; use one-colour outlines or Pencil or pen sketch for those.
    • Outlines only does not change single lines: they stay lines with a width.
    • The DXF is in millimetres unless you choose centimetres or inches; set the Width under More options to get the drawing at the size you want.

    More about what this tool reads and writes: Image Vectorizer.

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