[DrawBot] Given a circle radius and a pen thickness, create a spiral-ish path that fills a circle

plotter_circle_spiral.py

# 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)