Shape recognition is what the Shape Pen does. Draw with it and a rough sketch is matched against real shapes when you release, so a wobbly square becomes a proper square and a quick loop becomes a circle, no need to draw precisely.
Picking it
Open the palette's Draw category and choose Shape Pen (or press 6). Its neighbour, Freehand (P), is the same gesture with recognition off: it keeps your stroke exactly as you drew it.
There is no setting to remember and nothing to switch on. This used to be a magic-wand toggle in the Pencil's banner, which meant whether your next stroke would convert depended on a choice you might have made days ago on another device. Two pens put the answer where the decision is.
What it recognises
Your simplified stroke is scored against a handful of shapes, and if it is a confident enough match, a real shape is created instead of a freehand sketch:
- A rough four-corner outline becomes a square.
- A closed loop becomes a circle.
- A four-corner shape with corners at the edge midpoints becomes a diamond.
- A three-corner outline becomes a triangle.
- A five-pointed sketch becomes a star.
- A straight stroke becomes an arrow (a line with no arrowheads).
A few shapes are intentionally not recognised, such as trapezoids, speech bubbles, frames, and the device frames: they are either ambiguous to draw freehand or are not freehand-drawable, so they stay palette-only. If a stroke is not confidently matched, it simply commits as a normal freehand sketch.
How it decides
Recognition uses heuristics rather than template matching, measuring how closely your sample points hug each idealised shape, so it tolerates strokes drawn at any rotation or size. The confidence threshold leans toward converting: reaching for the Shape Pen rather than Freehand is itself the statement that you want strokes classified, and a false positive is a single undo away. The frustrating case is a wobbly square that stays a sketch when you wanted a real one, so the detector errs toward conversion.
Recognition only changes confident matches, so you can keep an irregular doodle as a genuine sketch with the Shape Pen too, then draw a deliberate square when you want it converted.
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