Sharpening#

At a glance#

• Auto-sharpen engine that recognizes intent (straight line, circle/ellipse, polygon, or freeform) and rebuilds an idealized, hand-drawn version.
  • Live sharpen (off by default) — beautify each stroke the moment you lift the pen.
  • Sharpen all — clean up an entire page (or a saved file) at once.
  • Sharpen settings panel — tune wobble, smoothing, circle snap, end taper, rotational symmetry (mandala mode), and text size.

Live sharpen and Sharpen all#

Live sharpen is off by default. Toggle it in the Quick Settings panel to beautify strokes automatically as you draw, or leave it off and use Sharpen all when you are ready. The Quick Settings panel also exposes wobble, smoothing, circle snap, end taper, rotational symmetry, and text size. Raising rotational symmetry above 1 fades the mandala guide axes in, and dropping it back to 1 fades them out.

How auto-sharpen works#

Each stroke runs through a four-stage pipeline:

1. Resample + denoise — even out the raw pointer samples and remove jitter (uniform resampling + Ramer–Douglas–Peucker simplification).
2. Recognize intent — classify the stroke as a line, circle/ellipse, polygon, or freeform curve (least-squares circle fit, corner detection, straightness test).
3. Rebuild — regenerate an idealized version of the detected shape while preserving its size, position, and winding direction.
4. Humanize — re-apply subtle, deterministic value-noise wobble, taper the stroke ends, and anchor endpoints so the result looks hand-drawn rather than mechanically perfect.
5. Fit — the result is kept as a few cubic Bézier anchors, fitted within a third of a pixel of it so the wobble survives, as a freehand stroke is when it is drawn. The rebuild used to draw ten points for every one it kept. Sharpen Selection fits what its sliders make the same way.

The engine is pure and deterministic (seeded from each stroke's id), so the same stroke sharpens identically whether it is processed live in the GUI or headless via napkin-sketch --sharpen.