Trace Modes¶
Vectorize traces an image in one of three modes, each suited to a different kind of source, plus a set of parameters that control fidelity and cleanup.
The three modes¶
A single threshold splits the image into ink and paper. Best for clean line art, inked scans, and logos. You choose what to trace:
- Fills — the filled black shapes are traced by Potrace (as in the other modes).
- Pencil line — the ink is thinned to a 1-px skeleton by Zhang–Suen thinning, then walked into real pencil strokes with variable width.
Pick either, or Both.
Segments the image into a few grey levels. Good for shaded pencil and tonal art where you want a handful of value bands rather than full colour.
Median-cut colour segmentation — one filled region per colour, so a flat-colour illustration becomes editable colour shapes. In Colour mode the Detail slider is the colour resolution (how finely the palette segments).
Parameters¶
| Control | What it does |
|---|---|
| Detail | Working resolution — higher resolves finer features (thin lines, tiny screws) and, in Colour mode, finer colour regions. Heavier at the top end. |
| Colours | (Grey/Colour) the number of quantised colours in the palette. Default 12. |
| Cleanup / Noise | Drops specks below this area — despeckle. Higher removes more small junk. |
| Corners | Corner sharpness — high keeps corners crisp, low rounds them (feeds Potrace's alphamax). |
| Smoothing | Bézier fit amount on the traced contours (the same Schneider fit the vector path uses). |
| Ignore background | Skips the border-dominant (background) colour so you don't trace the paper. |
| Trace | Pencil (centreline) · Fills · or Both. |
Colour fidelity¶
The palette is built with a farthest-point median-cut — it picks the most distinct colours, not just the biggest clusters, so a small but distinct feature (a coloured screw, an eye highlight) survives instead of being averaged into a neighbour. A light majority pass absorbs 1-pixel anti-aliased bands while keeping solid features.
Line art → B&W · flat colour → Colour
For inked line art use Black & White with Pencil line trace — it thins the ink to a skeleton and traces real variable-width pencil centrelines, not doubled filled outlines. It's the mode for turning a raster line drawing back into clean, editable pencil strokes. For a flat-colour illustration use Colour and raise Colours/Detail until the minority colours come through.
Potrace shines on flat colour & simple shapes — not tiny detail
Vectorizing is at its best on flat colours and simple shapes. Very fine, intricate detail (minuscule textures, delicate hatching, tiny features) traces poorly — the result either explodes into unmanageable geometry or loses the detail altogether. When that happens, don't force the trace:
- Keep it as a Bitmap — bring the image in as raster (Original or Toon Boom bitmap) and skip tracing entirely.
- Bring it in as true vectors another way — e.g. export the lines as SVG straight from Blender/Maya (Grease Pencil / Pencil+), so you get exact vectors with no tracing step at all.
- For fine line art specifically, B&W → Pencil line usually holds up far better than Colour/Grey fill tracing — it keeps thin linework as single centreline strokes instead of thickness-doubled outlines.
Everything is live
Every parameter re-traces on release, so you tune by eye in the Previewer. A scrub reuses the cached trace; only a param change re-runs it.