Notes
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The angle of a contour is computed as an average over *n* points along the contour.
If you obtain poor angles you can play with two variables: Change *n* via the **+w**
modifier to **-A**, and/or resample the contour via **-S**.  For a fixed *n* the
**-S** will localize the calculation, while the opposite is true if you increase *n*
for a constant **-S**.