/usr/lib/python2.7/dist-packages/ginga/util/bezier.py is in python-ginga 2.6.1-2.
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# bezier.py -- module for generating rasters of bezier curves
#
# This is open-source software licensed under a BSD license.
# Please see the file LICENSE.txt for details.
#
import math
# "reasonable" number of steps to make a smooth bezier curve
bezier_steps = 30
#
# See: http://caffeineoncode.com/2010/12/joining-multiple-bezier-curves/
#
# calculates points for a simple bezier curve with 4 control points
#
def get_4pt_bezier(steps, points):
"""Gets a series of bezier curve points with 1 set of 4
control points."""
for i in range(steps):
t = i / float(steps)
xloc = (math.pow(1-t, 3) * points[0][0] +
3 * t * math.pow(1-t, 2) * points[1][0] +
3 * (1-t) * math.pow(t, 2) * points[2][0] +
math.pow(t, 3) * points[3][0])
yloc = (math.pow(1-t, 3) * points[0][1] +
3 * t * math.pow(1-t, 2) * points[1][1] +
3 * (1-t) * math.pow(t, 2) * points[2][1] +
math.pow(t, 3) * points[3][1])
yield (xloc, yloc)
def get_bezier(steps, points):
"""Gets a series of bezier curve points with any number of sets
of 4 control points."""
res = []
num_pts = len(points)
for i in range(0, num_pts+1, 3):
if i + 4 < num_pts+1:
res.extend(list(get_4pt_bezier(steps, points[i:i+4])))
return res
def get_bezier_ellipse(x, y, xradius, yradius, kappa=0.5522848):
"""Get a set of 12 bezier control points necessary to form an
ellipse."""
xs, ys = x - xradius, y - yradius
ox, oy = xradius * kappa, yradius * kappa
xe, ye = x + xradius, y + yradius
pts = [(xs, y),
(xs, y - oy), (x - ox, ys), (x, ys),
(x + ox, ys), (xe, y - oy), (xe, y),
(xe, y + oy), (x + ox, ye), (x, ye),
(x - ox, ye), (xs, y + oy), (xs, y)]
return pts
# draws a smooth bezier curve by adding points that
# force smoothness
#
def get_smooth_bezier(steps, points):
newpoints = []
for i in range(len(points)):
# add the next point
newpoints.append(points[i])
if i % 2 == 0 and i > 0 and i+1 < len(points):
# calculate the midpoint
xloc = (points[i][0] + points[i+1][0]) / 2.0
yloc = (points[i][1] + points[i+1][1]) / 2.0
# add the new point
newpoints.append((xloc, yloc))
return get_bezier(steps, newpoints)
#END
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