design/invalid3.py

   1 #!/usr/bin/env python
   2 import sys;sys.path.insert(0, "..")
   3 from math import *
   4 from pyx import *
   5 # File for invalid parametrisations of Bezier curves
   6 # Some examples
   7
   8 def Dx_m(Dy):
   9     return (-1-2*Dy-sqrt((1+2*Dy)**2+3))/3.0
  10
  11 def Dx_p(Dy):
  12     return (-1-2*Dy+sqrt((1+2*Dy)**2+3))/3.0
  13
  14 def acurve(Dx_fct, Dy, Dx=None):
  15     if Dx is None:
  16         Dx = Dx_fct(Dy)
  17     p = path.curve(0,0, 0,1, Dx,1+Dy, 1,0)
  18     c = canvas.canvas()
  19     c.stroke(p, [deco.shownormpath()])
  20     c.text(-0.2, -10*unit.x_pt, r"\noindent$\Delta x=%g $\par\noindent$\Delta y=%g$"%(Dx,Dy),
  21            [text.parbox(4), text.size.footnotesize])
  22     return c
  23
  24 dx = 3
  25 dy = -3
  26 cc = acurve(Dx_m, 0)
  27 c = acurve(Dx_m, 1); cc.insert(c, [trafo.translate(dx, 0)])
  28 c = acurve(Dx_m, -1); cc.insert(c, [trafo.translate(2*dx, 0)])
  29 c = acurve(Dx_m, -2); cc.insert(c, [trafo.translate(0, dy)])
  30 c = acurve(Dx_p, -1); cc.insert(c, [trafo.translate(dx, dy)])
  31 c = acurve(Dx_p, -3); cc.insert(c, [trafo.translate(2*dx, dy)])
  32 cc.writePDFfile()
  33