OwlCyberSecurity - MANAGER

Edit File: bezier.py

""" A module providing some utility functions regarding bezier path manipulation. """ import numpy as np import matplotlib.cbook as cbook from matplotlib.path import Path class NonIntersectingPathException(ValueError): pass # some functions def get_intersection(cx1, cy1, cos_t1, sin_t1, cx2, cy2, cos_t2, sin_t2): """ Return the intersection between the line through (*cx1*, *cy1*) at angle *t1* and the line through (*cx2, cy2) at angle *t2*. """ # line1 => sin_t1 * (x - cx1) - cos_t1 * (y - cy1) = 0. # line1 => sin_t1 * x + cos_t1 * y = sin_t1*cx1 - cos_t1*cy1 line1_rhs = sin_t1 * cx1 - cos_t1 * cy1 line2_rhs = sin_t2 * cx2 - cos_t2 * cy2 # rhs matrix a, b = sin_t1, -cos_t1 c, d = sin_t2, -cos_t2 ad_bc = a * d - b * c if np.abs(ad_bc) < 1.0e-12: raise ValueError("Given lines do not intersect. Please verify that " "the angles are not equal or differ by 180 degrees.") # rhs_inverse a_, b_ = d, -b c_, d_ = -c, a a_, b_, c_, d_ = [k / ad_bc for k in [a_, b_, c_, d_]] x = a_ * line1_rhs + b_ * line2_rhs y = c_ * line1_rhs + d_ * line2_rhs return x, y def get_normal_points(cx, cy, cos_t, sin_t, length): """ For a line passing through (*cx*, *cy*) and having a angle *t*, return locations of the two points located along its perpendicular line at the distance of *length*. """ if length == 0.: return cx, cy, cx, cy cos_t1, sin_t1 = sin_t, -cos_t cos_t2, sin_t2 = -sin_t, cos_t x1, y1 = length * cos_t1 + cx, length * sin_t1 + cy x2, y2 = length * cos_t2 + cx, length * sin_t2 + cy return x1, y1, x2, y2 # BEZIER routines # subdividing bezier curve # http://www.cs.mtu.edu/~shene/COURSES/cs3621/NOTES/spline/Bezier/bezier-sub.html def _de_casteljau1(beta, t): next_beta = beta[:-1] * (1 - t) + beta[1:] * t return next_beta def split_de_casteljau(beta, t): """ Split a bezier segment defined by its control points *beta* into two separate segments divided at *t* and return their control points. """ beta = np.asarray(beta) beta_list = [beta] while True: beta = _de_casteljau1(beta, t) beta_list.append(beta) if len(beta) == 1: break left_beta = [beta[0] for beta in beta_list] right_beta = [beta[-1] for beta in reversed(beta_list)] return left_beta, right_beta @cbook._rename_parameter("3.1", "tolerence", "tolerance") def find_bezier_t_intersecting_with_closedpath( bezier_point_at_t, inside_closedpath, t0=0., t1=1., tolerance=0.01): """ Find a parameter t0 and t1 of the given bezier path which bounds the intersecting points with a provided closed path(*inside_closedpath*). Search starts from *t0* and *t1* and it uses a simple bisecting algorithm therefore one of the end point must be inside the path while the other doesn't. The search stop when |t0-t1| gets smaller than the given tolerance. value for - bezier_point_at_t : a function which returns x, y coordinates at *t* - inside_closedpath : return True if the point is inside the path """ # inside_closedpath : function start = bezier_point_at_t(t0) end = bezier_point_at_t(t1) start_inside = inside_closedpath(start) end_inside = inside_closedpath(end) if start_inside == end_inside and start != end: raise NonIntersectingPathException( "Both points are on the same side of the closed path") while True: # return if the distance is smaller than the tolerance if np.hypot(start[0] - end[0], start[1] - end[1]) < tolerance: return t0, t1 # calculate the middle point middle_t = 0.5 * (t0 + t1) middle = bezier_point_at_t(middle_t) middle_inside = inside_closedpath(middle) if start_inside ^ middle_inside: t1 = middle_t end = middle end_inside = middle_inside else: t0 = middle_t start = middle start_inside = middle_inside class BezierSegment(object): """ A simple class of a 2-dimensional bezier segment """ # Higher order bezier lines can be supported by simplying adding # corresponding values. _binom_coeff = {1: np.array([1., 1.]), 2: np.array([1., 2., 1.]), 3: np.array([1., 3., 3., 1.])} def __init__(self, control_points): """ *control_points* : location of contol points. It needs have a shape of n * 2, where n is the order of the bezier line. 1<= n <= 3 is supported. """ _o = len(control_points) self._orders = np.arange(_o) _coeff = BezierSegment._binom_coeff[_o - 1] xx, yy = np.asarray(control_points).T self._px = xx * _coeff self._py = yy * _coeff def point_at_t(self, t): "evaluate a point at t" tt = ((1 - t) ** self._orders)[::-1] * t ** self._orders _x = np.dot(tt, self._px) _y = np.dot(tt, self._py) return _x, _y @cbook._rename_parameter("3.1", "tolerence", "tolerance") def split_bezier_intersecting_with_closedpath( bezier, inside_closedpath, tolerance=0.01): """ bezier : control points of the bezier segment inside_closedpath : a function which returns true if the point is inside the path """ bz = BezierSegment(bezier) bezier_point_at_t = bz.point_at_t t0, t1 = find_bezier_t_intersecting_with_closedpath( bezier_point_at_t, inside_closedpath, tolerance=tolerance) _left, _right = split_de_casteljau(bezier, (t0 + t1) / 2.) return _left, _right @cbook.deprecated("3.1") @cbook._rename_parameter("3.1", "tolerence", "tolerance") def find_r_to_boundary_of_closedpath( inside_closedpath, xy, cos_t, sin_t, rmin=0., rmax=1., tolerance=0.01): """ Find a radius r (centered at *xy*) between *rmin* and *rmax* at which it intersect with the path. inside_closedpath : function cx, cy : center cos_t, sin_t : cosine and sine for the angle rmin, rmax : """ cx, cy = xy def _f(r): return cos_t * r + cx, sin_t * r + cy find_bezier_t_intersecting_with_closedpath( _f, inside_closedpath, t0=rmin, t1=rmax, tolerance=tolerance) # matplotlib specific @cbook._rename_parameter("3.1", "tolerence", "tolerance") def split_path_inout(path, inside, tolerance=0.01, reorder_inout=False): """ divide a path into two segment at the point where inside(x, y) becomes False. """ path_iter = path.iter_segments() ctl_points, command = next(path_iter) begin_inside = inside(ctl_points[-2:]) # true if begin point is inside ctl_points_old = ctl_points concat = np.concatenate iold = 0 i = 1 for ctl_points, command in path_iter: iold = i i += len(ctl_points) // 2 if inside(ctl_points[-2:]) != begin_inside: bezier_path = concat([ctl_points_old[-2:], ctl_points]) break ctl_points_old = ctl_points else: raise ValueError("The path does not intersect with the patch") bp = bezier_path.reshape((-1, 2)) left, right = split_bezier_intersecting_with_closedpath( bp, inside, tolerance) if len(left) == 2: codes_left = [Path.LINETO] codes_right = [Path.MOVETO, Path.LINETO] elif len(left) == 3: codes_left = [Path.CURVE3, Path.CURVE3] codes_right = [Path.MOVETO, Path.CURVE3, Path.CURVE3] elif len(left) == 4: codes_left = [Path.CURVE4, Path.CURVE4, Path.CURVE4] codes_right = [Path.MOVETO, Path.CURVE4, Path.CURVE4, Path.CURVE4] else: raise AssertionError("This should never be reached") verts_left = left[1:] verts_right = right[:] if path.codes is None: path_in = Path(concat([path.vertices[:i], verts_left])) path_out = Path(concat([verts_right, path.vertices[i:]])) else: path_in = Path(concat([path.vertices[:iold], verts_left]), concat([path.codes[:iold], codes_left])) path_out = Path(concat([verts_right, path.vertices[i:]]), concat([codes_right, path.codes[i:]])) if reorder_inout and not begin_inside: path_in, path_out = path_out, path_in return path_in, path_out def inside_circle(cx, cy, r): r2 = r ** 2 def _f(xy): x, y = xy return (x - cx) ** 2 + (y - cy) ** 2 < r2 return _f # quadratic bezier lines def get_cos_sin(x0, y0, x1, y1): dx, dy = x1 - x0, y1 - y0 d = (dx * dx + dy * dy) ** .5 # Account for divide by zero if d == 0: return 0.0, 0.0 return dx / d, dy / d @cbook._rename_parameter("3.1", "tolerence", "tolerance") def check_if_parallel(dx1, dy1, dx2, dy2, tolerance=1.e-5): """ returns * 1 if two lines are parallel in same direction * -1 if two lines are parallel in opposite direction * 0 otherwise """ theta1 = np.arctan2(dx1, dy1) theta2 = np.arctan2(dx2, dy2) dtheta = np.abs(theta1 - theta2) if dtheta < tolerance: return 1 elif np.abs(dtheta - np.pi) < tolerance: return -1 else: return False def get_parallels(bezier2, width): """ Given the quadratic bezier control points *bezier2*, returns control points of quadratic bezier lines roughly parallel to given one separated by *width*. """ # The parallel bezier lines are constructed by following ways. # c1 and c2 are control points representing the begin and end of the # bezier line. # cm is the middle point c1x, c1y = bezier2[0] cmx, cmy = bezier2[1] c2x, c2y = bezier2[2] parallel_test = check_if_parallel(c1x - cmx, c1y - cmy, cmx - c2x, cmy - c2y) if parallel_test == -1: cbook._warn_external( "Lines do not intersect. A straight line is used instead.") cos_t1, sin_t1 = get_cos_sin(c1x, c1y, c2x, c2y) cos_t2, sin_t2 = cos_t1, sin_t1 else: # t1 and t2 is the angle between c1 and cm, cm, c2. They are # also a angle of the tangential line of the path at c1 and c2 cos_t1, sin_t1 = get_cos_sin(c1x, c1y, cmx, cmy) cos_t2, sin_t2 = get_cos_sin(cmx, cmy, c2x, c2y) # find c1_left, c1_right which are located along the lines # through c1 and perpendicular to the tangential lines of the # bezier path at a distance of width. Same thing for c2_left and # c2_right with respect to c2. c1x_left, c1y_left, c1x_right, c1y_right = ( get_normal_points(c1x, c1y, cos_t1, sin_t1, width) ) c2x_left, c2y_left, c2x_right, c2y_right = ( get_normal_points(c2x, c2y, cos_t2, sin_t2, width) ) # find cm_left which is the intersecting point of a line through # c1_left with angle t1 and a line through c2_left with angle # t2. Same with cm_right. if parallel_test != 0: # a special case for a straight line, i.e., angle between two # lines are smaller than some (arbitrary) value. cmx_left, cmy_left = ( 0.5 * (c1x_left + c2x_left), 0.5 * (c1y_left + c2y_left) ) cmx_right, cmy_right = ( 0.5 * (c1x_right + c2x_right), 0.5 * (c1y_right + c2y_right) ) else: cmx_left, cmy_left = get_intersection(c1x_left, c1y_left, cos_t1, sin_t1, c2x_left, c2y_left, cos_t2, sin_t2) cmx_right, cmy_right = get_intersection(c1x_right, c1y_right, cos_t1, sin_t1, c2x_right, c2y_right, cos_t2, sin_t2) # the parallel bezier lines are created with control points of # [c1_left, cm_left, c2_left] and [c1_right, cm_right, c2_right] path_left = [(c1x_left, c1y_left), (cmx_left, cmy_left), (c2x_left, c2y_left)] path_right = [(c1x_right, c1y_right), (cmx_right, cmy_right), (c2x_right, c2y_right)] return path_left, path_right def find_control_points(c1x, c1y, mmx, mmy, c2x, c2y): """ Find control points of the Bezier curve passing through (*c1x*, *c1y*), (*mmx*, *mmy*), and (*c2x*, *c2y*), at parametric values 0, 0.5, and 1. """ cmx = .5 * (4 * mmx - (c1x + c2x)) cmy = .5 * (4 * mmy - (c1y + c2y)) return [(c1x, c1y), (cmx, cmy), (c2x, c2y)] def make_wedged_bezier2(bezier2, width, w1=1., wm=0.5, w2=0.): """ Being similar to get_parallels, returns control points of two quadratic bezier lines having a width roughly parallel to given one separated by *width*. """ # c1, cm, c2 c1x, c1y = bezier2[0] cmx, cmy = bezier2[1] c3x, c3y = bezier2[2] # t1 and t2 is the angle between c1 and cm, cm, c3. # They are also a angle of the tangential line of the path at c1 and c3 cos_t1, sin_t1 = get_cos_sin(c1x, c1y, cmx, cmy) cos_t2, sin_t2 = get_cos_sin(cmx, cmy, c3x, c3y) # find c1_left, c1_right which are located along the lines # through c1 and perpendicular to the tangential lines of the # bezier path at a distance of width. Same thing for c3_left and # c3_right with respect to c3. c1x_left, c1y_left, c1x_right, c1y_right = ( get_normal_points(c1x, c1y, cos_t1, sin_t1, width * w1) ) c3x_left, c3y_left, c3x_right, c3y_right = ( get_normal_points(c3x, c3y, cos_t2, sin_t2, width * w2) ) # find c12, c23 and c123 which are middle points of c1-cm, cm-c3 and # c12-c23 c12x, c12y = (c1x + cmx) * .5, (c1y + cmy) * .5 c23x, c23y = (cmx + c3x) * .5, (cmy + c3y) * .5 c123x, c123y = (c12x + c23x) * .5, (c12y + c23y) * .5 # tangential angle of c123 (angle between c12 and c23) cos_t123, sin_t123 = get_cos_sin(c12x, c12y, c23x, c23y) c123x_left, c123y_left, c123x_right, c123y_right = ( get_normal_points(c123x, c123y, cos_t123, sin_t123, width * wm) ) path_left = find_control_points(c1x_left, c1y_left, c123x_left, c123y_left, c3x_left, c3y_left) path_right = find_control_points(c1x_right, c1y_right, c123x_right, c123y_right, c3x_right, c3y_right) return path_left, path_right def make_path_regular(p): """ If the :attr:`codes` attribute of `Path` *p* is None, return a copy of *p* with the :attr:`codes` set to (MOVETO, LINETO, LINETO, ..., LINETO); otherwise return *p* itself. """ c = p.codes if c is None: c = np.full(len(p.vertices), Path.LINETO, dtype=Path.code_type) c[0] = Path.MOVETO return Path(p.vertices, c) else: return p def concatenate_paths(paths): """Concatenate a list of paths into a single path.""" vertices = np.concatenate([p.vertices for p in paths]) codes = np.concatenate([make_path_regular(p).codes for p in paths]) return Path(vertices, codes)