def apply_blade_offset(self, poly, offset):
""" Apply blade offset to the given polygon by appending a quadratic
bezier to each point .
"""
# Use a QPainterPath to track the distance in c++
path = QPainterPath()
cutoff = cos(radians(self.config.cutoff)) # Forget
last = None
n = len(poly)
for i, p in enumerate(poly):
if i == 0:
path.moveTo(p)
last_path = QPainterPath()
last_path.moveTo(p)
last = p
continue
# Move to the point
path.lineTo(p)
if i+1 == n:
# Done
break
# Get next point
next = poly.at(i+1)
# Make our paths
last_path.lineTo(p)
next_path = QPainterPath()
next_path.moveTo(p)
next_path.lineTo(next)
# Get angle between the two components
u, v = QVector2D(last-p), QVector2D(next-p)
cos_theta = QVector2D.dotProduct(u.normalized(), v.normalized())
# If the angle is large enough to need compensation
if (cos_theta < cutoff and
last_path.length() > offset and
next_path.length() > offset):
# Calculate the extended point
t = last_path.percentAtLength(offset)
c1 = p+(last_path.pointAtPercent(t)-last)
c2 = p
t = next_path.percentAtLength(offset)
ep = next_path.pointAtPercent(t)
if offset > 2:
# Can smooth it for larger offsets
path.cubicTo(c1, c2, ep)
else:
# This works for small offsets < 0.5 mm
path.lineTo(c1)
path.lineTo(ep)
# Update last
last_path = next_path
last = p
return path.toSubpathPolygons(IDENITY_MATRIX)
def process_cubic(self, offset_path, blade_path, params, quality):
""" Add offset correction to a cubic bezier.
"""
r = self.config.offset
p0 = blade_path.currentPosition()
p1, p2, p3 = params
self.add_continuity_correction(offset_path, blade_path, p1)
curve = QPainterPath()
curve.moveTo(p0)
curve.cubicTo(*params)
p = QPainterPath()
p.moveTo(p0)
if quality == 1:
polygon = curve.toSubpathPolygons(IDENITY_MATRIX)[0]
else:
m = QTransform.fromScale(quality, quality)
m_inv = QTransform.fromScale(1/quality, 1/quality)
polygon = m_inv.map(curve.toSubpathPolygons(m)[0])
for point in polygon:
p.lineTo(point)
t = curve.percentAtLength(p.length())
angle = curve.angleAtPercent(t)
a = radians(angle)
dx, dy = r*cos(a), -r*sin(a)
offset_path.lineTo(point.x()+dx, point.y()+dy)
blade_path.cubicTo(*params)
