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#!/usr/bin/env python
'''
Copyright (C) 2005 Aaron Spike, aaron@ekips.org
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
drawwave() was translated into python from the postscript version
described at http://www.ghostscript.com/person/toby/ and located
at http://www.telegraphics.com.au/sw/sine.ps .
http://www.tinaja.com/glib/bezsine.pdf shows another method for
approximating sine with beziers.
The orginal postscript version displayed the following copyright
notice and was released under the terms of the GPL:
Copyright (C) 2001-3 Toby Thain, toby@telegraphics.com.au
'''
import inkex, simplepath, simplestyle
from math import *
from random import *
def drawwave(samples, periods, width, height, left, top,
fx = "sin(x)", fpx = "cos(x)", fponum = True):
# step is the distance between nodes on x
step = 2*pi / samples
third = step / 3.0
# coords and scales based on the source rect
xoff = left
yoff = top + (height / 2)
scalex = width / (2*pi * periods)
scaley = height / 2
procx = lambda x: x * scalex + xoff
procy = lambda y: y * scaley + yoff
# functions specified by the user
if fx != "":
f = eval('lambda x: ' + fx)
if fpx != "":
fp = eval('lambda x: ' + fpx)
# initialize function and derivative for 0;
# they are carried over from one iteration to the next, to avoid extra function calculations
y0 = f(0)
if fponum == True: # numerical derivative, using 0.001*step as the small differential
d0 = (f(0 + 0.001*step) - y0)/(0.001*step)
else: # derivative given by the user
d0 = fp(0)
a = [] # path array
a.append(['M',[procx(0.0), procy(y0)]]) # initial moveto
for i in range(int(samples * periods)):
x = i * step
y1 = f(x + step)
if fponum == True: # numerical derivative
d1 = (y1 - f(x + step - 0.001*step))/(0.001*step)
else: # derivative given by the user
d1 = fp(x + step)
# create curve
a.append(['C',[procx(x + third), procy(y0 + (d0 * third)),
procx(x + (step - third)), procy(y1 - (d1 * third)),
procx(x + step), procy(y1)]])
y0 = y1 # next segment's y0 is this segment's y1
d0 = d1 # we assume the function is smooth everywhere, so carry over the derivative too
return a
class Wavy(inkex.Effect):
def __init__(self):
inkex.Effect.__init__(self)
self.OptionParser.add_option("-p", "--periods",
action="store", type="float",
dest="periods", default=4.0,
help="Periods (2*Pi each)")
self.OptionParser.add_option("-s", "--samples",
action="store", type="int",
dest="samples", default=8,
help="Samples per period")
self.OptionParser.add_option("--fofx",
action="store", type="string",
dest="fofx", default="sin(x)",
help="f(x) for plotting")
self.OptionParser.add_option("--fponum",
action="store", type="inkbool",
dest="fponum", default=True,
help="Calculate the first derivative numerically")
self.OptionParser.add_option("--fpofx",
action="store", type="string",
dest="fpofx", default="cos(x)",
help="f'(x) for plotting")
def effect(self):
for id, node in self.selected.iteritems():
if node.tagName == 'rect':
new = self.document.createElement('svg:path')
x = float(node.attributes.getNamedItem('x').value)
y = float(node.attributes.getNamedItem('y').value)
w = float(node.attributes.getNamedItem('width').value)
h = float(node.attributes.getNamedItem('height').value)
s = node.attributes.getNamedItem('style').value
new.setAttribute('style', s)
try:
t = node.attributes.getNamedItem('transform').value
new.setAttribute('transform', t)
except AttributeError:
pass
new.setAttribute('d', simplepath.formatPath(
drawwave(self.options.samples,
self.options.periods,
w,h,x,y,
self.options.fofx,
self.options.fpofx,
self.options.fponum)))
node.parentNode.appendChild(new)
node.parentNode.removeChild(node)
e = Wavy()
e.affect()
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