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@justvanrossum
Created December 8, 2021 21:12
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[DrawBot] Given a circle radius and a pen thickness, create a spiral-ish path that fills a circle
# https://twitter.com/rosettatype/status/1468660017993854980
def plotter_circle_spiral(bez, center, radius, penWidth):
H = 0.5522847498 # Bezier circle magic constant
radius -= penWidth / 2
numRevolutions = ceil(radius / penWidth + 1)
xRadius = yRadius = radius
radiusDelta = radius / (numRevolutions - 1)
cx, cy = center
bez.moveTo((cx + radius, cy))
dx, dy = 1, 0
for i in range(4 * numRevolutions):
h1x = xRadius * (dx - dy * H)
h1y = yRadius * (dy + dx * H)
h2x = xRadius * (-dy + dx * H)
h2y = yRadius * (dx + dy * H)
x = xRadius * -dy
y = yRadius * dx
bez.curveTo((cx + h1x, cy + h1y), (cx + h2x, cy + h2y), (cx + x, cy + y))
dx, dy = -dy, dx
if not (i + 1) % 4:
yRadius -= radiusDelta
if i > 2 and not i % 4:
xRadius -= radiusDelta
radius = 320
penWidth = 130
bez = BezierPath()
plotter_circle_spiral(bez, (500, 500), radius, penWidth)
lineJoin("round")
lineCap("round")
fill(None)
stroke(0.8)
strokeWidth(penWidth)
drawPath(bez)
stroke(0)
strokeWidth(2)
drawPath(bez)
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