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490 lines
15 KiB
490 lines
15 KiB
"""
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A module providing some utility functions regarding bezier path manipulation.
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"""
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import warnings
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import numpy as np
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from matplotlib.path import Path
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class NonIntersectingPathException(ValueError):
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pass
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# some functions
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def get_intersection(cx1, cy1, cos_t1, sin_t1,
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cx2, cy2, cos_t2, sin_t2):
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""" return a intersecting point between a line through (cx1, cy1)
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and having angle t1 and a line through (cx2, cy2) and angle t2.
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"""
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# line1 => sin_t1 * (x - cx1) - cos_t1 * (y - cy1) = 0.
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# line1 => sin_t1 * x + cos_t1 * y = sin_t1*cx1 - cos_t1*cy1
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line1_rhs = sin_t1 * cx1 - cos_t1 * cy1
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line2_rhs = sin_t2 * cx2 - cos_t2 * cy2
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# rhs matrix
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a, b = sin_t1, -cos_t1
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c, d = sin_t2, -cos_t2
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ad_bc = a * d - b * c
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if np.abs(ad_bc) < 1.0e-12:
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raise ValueError("Given lines do not intersect. Please verify that "
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"the angles are not equal or differ by 180 degrees.")
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# rhs_inverse
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a_, b_ = d, -b
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c_, d_ = -c, a
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a_, b_, c_, d_ = [k / ad_bc for k in [a_, b_, c_, d_]]
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x = a_ * line1_rhs + b_ * line2_rhs
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y = c_ * line1_rhs + d_ * line2_rhs
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return x, y
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def get_normal_points(cx, cy, cos_t, sin_t, length):
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"""
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For a line passing through (*cx*, *cy*) and having a angle *t*, return
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locations of the two points located along its perpendicular line at the
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distance of *length*.
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"""
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if length == 0.:
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return cx, cy, cx, cy
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cos_t1, sin_t1 = sin_t, -cos_t
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cos_t2, sin_t2 = -sin_t, cos_t
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x1, y1 = length * cos_t1 + cx, length * sin_t1 + cy
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x2, y2 = length * cos_t2 + cx, length * sin_t2 + cy
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return x1, y1, x2, y2
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# BEZIER routines
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# subdividing bezier curve
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# http://www.cs.mtu.edu/~shene/COURSES/cs3621/NOTES/spline/Bezier/bezier-sub.html
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def _de_casteljau1(beta, t):
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next_beta = beta[:-1] * (1 - t) + beta[1:] * t
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return next_beta
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def split_de_casteljau(beta, t):
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"""split a bezier segment defined by its controlpoints *beta*
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into two separate segment divided at *t* and return their control points.
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"""
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beta = np.asarray(beta)
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beta_list = [beta]
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while True:
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beta = _de_casteljau1(beta, t)
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beta_list.append(beta)
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if len(beta) == 1:
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break
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left_beta = [beta[0] for beta in beta_list]
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right_beta = [beta[-1] for beta in reversed(beta_list)]
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return left_beta, right_beta
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# FIXME spelling mistake in the name of the parameter ``tolerence``
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def find_bezier_t_intersecting_with_closedpath(bezier_point_at_t,
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inside_closedpath,
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t0=0., t1=1., tolerence=0.01):
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""" Find a parameter t0 and t1 of the given bezier path which
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bounds the intersecting points with a provided closed
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path(*inside_closedpath*). Search starts from *t0* and *t1* and it
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uses a simple bisecting algorithm therefore one of the end point
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must be inside the path while the orther doesn't. The search stop
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when |t0-t1| gets smaller than the given tolerence.
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value for
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- bezier_point_at_t : a function which returns x, y coordinates at *t*
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- inside_closedpath : return True if the point is inside the path
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"""
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# inside_closedpath : function
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start = bezier_point_at_t(t0)
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end = bezier_point_at_t(t1)
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start_inside = inside_closedpath(start)
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end_inside = inside_closedpath(end)
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if start_inside == end_inside and start != end:
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raise NonIntersectingPathException(
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"Both points are on the same side of the closed path")
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while True:
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# return if the distance is smaller than the tolerence
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if np.hypot(start[0] - end[0], start[1] - end[1]) < tolerence:
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return t0, t1
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# calculate the middle point
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middle_t = 0.5 * (t0 + t1)
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middle = bezier_point_at_t(middle_t)
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middle_inside = inside_closedpath(middle)
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if start_inside ^ middle_inside:
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t1 = middle_t
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end = middle
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end_inside = middle_inside
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else:
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t0 = middle_t
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start = middle
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start_inside = middle_inside
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class BezierSegment(object):
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"""
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A simple class of a 2-dimensional bezier segment
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"""
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# Higher order bezier lines can be supported by simplying adding
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# corresponding values.
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_binom_coeff = {1: np.array([1., 1.]),
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2: np.array([1., 2., 1.]),
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3: np.array([1., 3., 3., 1.])}
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def __init__(self, control_points):
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"""
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*control_points* : location of contol points. It needs have a
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shpae of n * 2, where n is the order of the bezier line. 1<=
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n <= 3 is supported.
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"""
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_o = len(control_points)
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self._orders = np.arange(_o)
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_coeff = BezierSegment._binom_coeff[_o - 1]
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xx, yy = np.asarray(control_points).T
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self._px = xx * _coeff
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self._py = yy * _coeff
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def point_at_t(self, t):
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"evaluate a point at t"
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tt = ((1 - t) ** self._orders)[::-1] * t ** self._orders
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_x = np.dot(tt, self._px)
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_y = np.dot(tt, self._py)
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return _x, _y
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def split_bezier_intersecting_with_closedpath(bezier,
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inside_closedpath,
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tolerence=0.01):
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"""
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bezier : control points of the bezier segment
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inside_closedpath : a function which returns true if the point is inside
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the path
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"""
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bz = BezierSegment(bezier)
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bezier_point_at_t = bz.point_at_t
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t0, t1 = find_bezier_t_intersecting_with_closedpath(bezier_point_at_t,
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inside_closedpath,
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tolerence=tolerence)
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_left, _right = split_de_casteljau(bezier, (t0 + t1) / 2.)
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return _left, _right
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def find_r_to_boundary_of_closedpath(inside_closedpath, xy,
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cos_t, sin_t,
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rmin=0., rmax=1., tolerence=0.01):
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"""
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Find a radius r (centered at *xy*) between *rmin* and *rmax* at
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which it intersect with the path.
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inside_closedpath : function
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cx, cy : center
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cos_t, sin_t : cosine and sine for the angle
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rmin, rmax :
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"""
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cx, cy = xy
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def _f(r):
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return cos_t * r + cx, sin_t * r + cy
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find_bezier_t_intersecting_with_closedpath(_f, inside_closedpath,
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t0=rmin, t1=rmax,
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tolerence=tolerence)
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# matplotlib specific
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def split_path_inout(path, inside, tolerence=0.01, reorder_inout=False):
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""" divide a path into two segment at the point where inside(x, y)
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becomes False.
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"""
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path_iter = path.iter_segments()
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ctl_points, command = next(path_iter)
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begin_inside = inside(ctl_points[-2:]) # true if begin point is inside
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ctl_points_old = ctl_points
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concat = np.concatenate
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iold = 0
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i = 1
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for ctl_points, command in path_iter:
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iold = i
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i += len(ctl_points) // 2
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if inside(ctl_points[-2:]) != begin_inside:
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bezier_path = concat([ctl_points_old[-2:], ctl_points])
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break
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ctl_points_old = ctl_points
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else:
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raise ValueError("The path does not intersect with the patch")
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bp = bezier_path.reshape((-1, 2))
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left, right = split_bezier_intersecting_with_closedpath(
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bp, inside, tolerence)
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if len(left) == 2:
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codes_left = [Path.LINETO]
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codes_right = [Path.MOVETO, Path.LINETO]
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elif len(left) == 3:
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codes_left = [Path.CURVE3, Path.CURVE3]
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codes_right = [Path.MOVETO, Path.CURVE3, Path.CURVE3]
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elif len(left) == 4:
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codes_left = [Path.CURVE4, Path.CURVE4, Path.CURVE4]
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codes_right = [Path.MOVETO, Path.CURVE4, Path.CURVE4, Path.CURVE4]
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else:
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raise AssertionError("This should never be reached")
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verts_left = left[1:]
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verts_right = right[:]
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if path.codes is None:
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path_in = Path(concat([path.vertices[:i], verts_left]))
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path_out = Path(concat([verts_right, path.vertices[i:]]))
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else:
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path_in = Path(concat([path.vertices[:iold], verts_left]),
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concat([path.codes[:iold], codes_left]))
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path_out = Path(concat([verts_right, path.vertices[i:]]),
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concat([codes_right, path.codes[i:]]))
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if reorder_inout and begin_inside is False:
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path_in, path_out = path_out, path_in
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return path_in, path_out
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def inside_circle(cx, cy, r):
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r2 = r ** 2
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def _f(xy):
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x, y = xy
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return (x - cx) ** 2 + (y - cy) ** 2 < r2
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return _f
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# quadratic bezier lines
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def get_cos_sin(x0, y0, x1, y1):
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dx, dy = x1 - x0, y1 - y0
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d = (dx * dx + dy * dy) ** .5
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# Account for divide by zero
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if d == 0:
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return 0.0, 0.0
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return dx / d, dy / d
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def check_if_parallel(dx1, dy1, dx2, dy2, tolerence=1.e-5):
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""" returns
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* 1 if two lines are parralel in same direction
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* -1 if two lines are parralel in opposite direction
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* 0 otherwise
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"""
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theta1 = np.arctan2(dx1, dy1)
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theta2 = np.arctan2(dx2, dy2)
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dtheta = np.abs(theta1 - theta2)
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if dtheta < tolerence:
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return 1
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elif np.abs(dtheta - np.pi) < tolerence:
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return -1
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else:
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return False
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def get_parallels(bezier2, width):
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"""
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Given the quadratic bezier control points *bezier2*, returns
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control points of quadratic bezier lines roughly parallel to given
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one separated by *width*.
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"""
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# The parallel bezier lines are constructed by following ways.
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# c1 and c2 are control points representing the begin and end of the
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# bezier line.
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# cm is the middle point
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c1x, c1y = bezier2[0]
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cmx, cmy = bezier2[1]
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c2x, c2y = bezier2[2]
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parallel_test = check_if_parallel(c1x - cmx, c1y - cmy,
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cmx - c2x, cmy - c2y)
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if parallel_test == -1:
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warnings.warn(
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"Lines do not intersect. A straight line is used instead.")
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cos_t1, sin_t1 = get_cos_sin(c1x, c1y, c2x, c2y)
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cos_t2, sin_t2 = cos_t1, sin_t1
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else:
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# t1 and t2 is the angle between c1 and cm, cm, c2. They are
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# also a angle of the tangential line of the path at c1 and c2
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cos_t1, sin_t1 = get_cos_sin(c1x, c1y, cmx, cmy)
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cos_t2, sin_t2 = get_cos_sin(cmx, cmy, c2x, c2y)
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# find c1_left, c1_right which are located along the lines
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# through c1 and perpendicular to the tangential lines of the
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# bezier path at a distance of width. Same thing for c2_left and
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# c2_right with respect to c2.
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c1x_left, c1y_left, c1x_right, c1y_right = (
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get_normal_points(c1x, c1y, cos_t1, sin_t1, width)
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)
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c2x_left, c2y_left, c2x_right, c2y_right = (
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get_normal_points(c2x, c2y, cos_t2, sin_t2, width)
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)
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# find cm_left which is the intersectng point of a line through
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# c1_left with angle t1 and a line through c2_left with angle
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# t2. Same with cm_right.
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if parallel_test != 0:
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# a special case for a straight line, i.e., angle between two
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# lines are smaller than some (arbitrtay) value.
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cmx_left, cmy_left = (
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0.5 * (c1x_left + c2x_left), 0.5 * (c1y_left + c2y_left)
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)
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cmx_right, cmy_right = (
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0.5 * (c1x_right + c2x_right), 0.5 * (c1y_right + c2y_right)
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)
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else:
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cmx_left, cmy_left = get_intersection(c1x_left, c1y_left, cos_t1,
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sin_t1, c2x_left, c2y_left,
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cos_t2, sin_t2)
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cmx_right, cmy_right = get_intersection(c1x_right, c1y_right, cos_t1,
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sin_t1, c2x_right, c2y_right,
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cos_t2, sin_t2)
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# the parallel bezier lines are created with control points of
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# [c1_left, cm_left, c2_left] and [c1_right, cm_right, c2_right]
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path_left = [(c1x_left, c1y_left),
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(cmx_left, cmy_left),
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(c2x_left, c2y_left)]
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path_right = [(c1x_right, c1y_right),
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(cmx_right, cmy_right),
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(c2x_right, c2y_right)]
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return path_left, path_right
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def find_control_points(c1x, c1y, mmx, mmy, c2x, c2y):
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""" Find control points of the bezier line through c1, mm, c2. We
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simply assume that c1, mm, c2 which have parametric value 0, 0.5, and 1.
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"""
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cmx = .5 * (4 * mmx - (c1x + c2x))
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cmy = .5 * (4 * mmy - (c1y + c2y))
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return [(c1x, c1y), (cmx, cmy), (c2x, c2y)]
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def make_wedged_bezier2(bezier2, width, w1=1., wm=0.5, w2=0.):
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"""
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Being similar to get_parallels, returns control points of two quadrativ
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bezier lines having a width roughly parallel to given one separated by
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*width*.
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"""
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# c1, cm, c2
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c1x, c1y = bezier2[0]
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cmx, cmy = bezier2[1]
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c3x, c3y = bezier2[2]
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# t1 and t2 is the angle between c1 and cm, cm, c3.
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# They are also a angle of the tangential line of the path at c1 and c3
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cos_t1, sin_t1 = get_cos_sin(c1x, c1y, cmx, cmy)
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cos_t2, sin_t2 = get_cos_sin(cmx, cmy, c3x, c3y)
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# find c1_left, c1_right which are located along the lines
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# through c1 and perpendicular to the tangential lines of the
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# bezier path at a distance of width. Same thing for c3_left and
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# c3_right with respect to c3.
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c1x_left, c1y_left, c1x_right, c1y_right = (
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get_normal_points(c1x, c1y, cos_t1, sin_t1, width * w1)
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)
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c3x_left, c3y_left, c3x_right, c3y_right = (
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get_normal_points(c3x, c3y, cos_t2, sin_t2, width * w2)
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)
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# find c12, c23 and c123 which are middle points of c1-cm, cm-c3 and
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# c12-c23
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c12x, c12y = (c1x + cmx) * .5, (c1y + cmy) * .5
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c23x, c23y = (cmx + c3x) * .5, (cmy + c3y) * .5
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c123x, c123y = (c12x + c23x) * .5, (c12y + c23y) * .5
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# tangential angle of c123 (angle between c12 and c23)
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cos_t123, sin_t123 = get_cos_sin(c12x, c12y, c23x, c23y)
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c123x_left, c123y_left, c123x_right, c123y_right = (
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get_normal_points(c123x, c123y, cos_t123, sin_t123, width * wm)
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)
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path_left = find_control_points(c1x_left, c1y_left,
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c123x_left, c123y_left,
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c3x_left, c3y_left)
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path_right = find_control_points(c1x_right, c1y_right,
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c123x_right, c123y_right,
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c3x_right, c3y_right)
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return path_left, path_right
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def make_path_regular(p):
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"""
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fill in the codes if None.
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"""
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c = p.codes
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if c is None:
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c = np.empty(p.vertices.shape[:1], "i")
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c.fill(Path.LINETO)
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c[0] = Path.MOVETO
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return Path(p.vertices, c)
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else:
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return p
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def concatenate_paths(paths):
|
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"""
|
|
concatenate list of paths into a single path.
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|
"""
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|
|
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vertices = []
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|
codes = []
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for p in paths:
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|
p = make_path_regular(p)
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|
vertices.append(p.vertices)
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|
codes.append(p.codes)
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|
|
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_path = Path(np.concatenate(vertices),
|
|
np.concatenate(codes))
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|
return _path
|