def intersection(p0, p1, l):
# get the intersection of two parabolas
p = p0
if p0.x == p1.x:
py = (p0.y + p1.y) / 2.0
elif p1.x == l:
py = p1.y
elif p0.x == l:
py = p0.y
p = p1
else:
# use quadratic formula
z0 = 2.0 * (p0.x - l)
z1 = 2.0 * (p1.x - l)
a = 1.0 / z0 - 1.0 / z1
b = -2.0 * (p0.y / z0 - p1.y / z1)
c = 1.0 * (p0.y**2 + p0.x**2 -
l**2) / z0 - 1.0 * (p1.y**2 + p1.x**2 - l**2) / z1
py = 1.0 * (-b - math.sqrt(b * b - 4 * a * c)) / (2 * a)
px = 1.0 * (p.x**2 + (p.y - py)**2 - l**2) / (2 * p.x - 2 * l)
res = Point(px, py)
return res
def circle(self, a, b, c):
if ((b.x - a.x) * (c.y - a.y) - (c.x - a.x) * (b.y - a.y)) > 0:
return False, None, None
# Joseph O'Rourke, Computational Geometry in C (2nd ed.) p.189
A = b.x - a.x
B = b.y - a.y
C = c.x - a.x
D = c.y - a.y
E = A * (a.x + b.x) + B * (a.y + b.y)
F = C * (a.x + c.x) + D * (a.y + c.y)
G = 2 * (A * (c.y - b.y) - B * (c.x - b.x))
if G == 0:
return False, None, None # Points are co-linear
# point o is the center of the circle
ox = 1.0 * (D * E - B * F) / G
oy = 1.0 * (A * F - C * E) / G
# o.x plus radius equals max x coord
x = ox + math.sqrt((a.x - ox)**2 + (a.y - oy)**2)
o = Point(ox, oy)
return True, x, o
def bresenham_line(p1, p2):
x0 = p1.x
x1 = p2.x
y0 = p1.y
y1 = p2.y
dx = x1 - x0
dy = y1 - y0
xsign = 1 if dx > 0 else -1
ysign = 1 if dy > 0 else -1
dx = abs(dx)
dy = abs(dy)
if dx > dy:
xx, xy, yx, yy = xsign, 0, 0, ysign
else:
dx, dy = dy, dx
xx, xy, yx, yy = 0, ysign, xsign, 0
D = 2 * dy - dx
y = 0
for x in range(dx + 1):
yield Point(x0 + x * xx + y * yx, y0 + x * xy + y * yy)
if D > 0:
y += 1
D -= dx
D += dy
def __init__(self, points, check=True):
self.points = [Point(*x) for x in points]
if len(self.points) < 3:
raise ValueError('Not a polygon')
self.edges = self.gen_edges()
if check and not (self.check_convex()
and self.check_self_intersection()
and self.check_num_of_edges()):
raise ValueError('Not convex')
self.bbb = []
self.circles = None
def voronoi(self):
test = set()
for e in self.edges:
i = 0
for u in bresenham_line(*e.points):
if i % 20 == 0:
test.add(u)
i += 1
v = Voronoi(test)
v.process()
self.bbb = []
voronoi_res = []
ddd = {}
for e in v.output:
p01 = round(e.points[0].x), round(e.points[0].y)
p02 = round(e.points[1].x), round(e.points[1].y)
if p01 == p02:
continue
if p01 in ddd:
ddd[p01] += 1
else:
ddd[p01] = 1
p1 = Point(*p01)
p2 = Point(*p02)
voronoi_res.append(Segment(p1, p2))
for e in voronoi_res:
p1 = e.points[0]
p2 = e.points[1]
if self.check_point_inside_polygon(p1) and \
self.check_point_inside_polygon(p2) and \
not self.check_point_on_edge(p1) and \
not self.check_point_on_edge(p2):
self.bbb.append(e)
self.filter_bbb(voronoi_res, ddd)
def read_points(filename):
book = open_workbook(filename)
position_sheet = book.sheet_by_index(0)
value_sheet = book.sheet_by_index(1)
d = dict()
for row in range(1, position_sheet.nrows):
key = position_sheet.cell(row, 0).value
x = position_sheet.cell(row, 1).value
y = position_sheet.cell(row, 2).value
d[key] = Point(key, x, y)
for row in range(1, value_sheet.nrows):
key = value_sheet.cell(row, 0).value
val = value_sheet.cell(row, 1).value
d[key].val = val
return d.values()
def arc_insert(self, p):
if self.arc is None:
self.arc = Arc(p)
else:
i = self.arc
while i is not None:
flag, z = self.intersect(p, i)
if flag:
flag, zz = self.intersect(p, i.pnext)
if (i.pnext is not None) and (not flag):
i.pnext.pprev = Arc(i.p, i, i.pnext)
i.pnext = i.pnext.pprev
else:
i.pnext = Arc(i.p, i)
i.pnext.s1 = i.s1
i.pnext.pprev = Arc(p, i, i.pnext)
i.pnext = i.pnext.pprev
i = i.pnext # now i points to the new arc
seg = Segment(z, None)
self.output.append(seg)
i.pprev.s1 = i.s0 = seg
seg = Segment(z, None)
self.output.append(seg)
i.pnext.s0 = i.s1 = seg
self.check_circle_event(i)
self.check_circle_event(i.pprev)
self.check_circle_event(i.pnext)
return
i = i.pnext
i = self.arc
while i.pnext is not None:
i = i.pnext
i.pnext = Arc(p, i)
# insert new segment between p and i
x = self.x0
y = (i.pnext.p.y + i.p.y) / 2.0
start = Point(x, y)
seg = Segment(start, None)
i.s1 = i.pnext.s0 = seg
self.output.append(seg)
def intersect(self, p, i):
# check whether a new parabola at point p intersect with arc i
if i is None:
return False, None
if i.p.x == p.x:
return False, None
a = 0.0
b = 0.0
if i.pprev is not None:
a = (self.intersection(i.pprev.p, i.p, 1.0 * p.x)).y
if i.pnext is not None:
b = (self.intersection(i.p, i.pnext.p, 1.0 * p.x)).y
if (((i.pprev is None) or (a <= p.y))
and ((i.pnext is None) or (p.y <= b))):
py = p.y
px = 1.0 * (i.p.x**2 +
(i.p.y - py)**2 - p.x**2) / (2 * i.p.x - 2 * p.x)
res = Point(px, py)
return True, res
return False, None