examples/tree.py

   1 # fractal tree
   2 # contributed by Gerhard Schmid and André Wobst
   3
   4 # extend module search path - not needed when PyX is installed properly
   5 import sys; sys.path[:0] = [".."]
   6
   7 from pyx import *
   8
   9 # base tree length
  10 l = 5
  11
  12 # base transformations for the left, center, and right part of the tree
  13 ltrafo = trafo.rotate(65).scaled(0.4).translated(0, l * 2.0 / 3.0)
  14 ctrafo = trafo.rotate(-4).scaled(0.75).translated(0, l)
  15 rtrafo = trafo.mirror(90).rotated(-65).scaled(0.35).translated(0, l)
  16
  17 def tree(depth):
  18     "return transformations for a recursive tree of given depth"
  19     r = [trafo.rotate(5)]
  20     if depth > 0:
  21         subtree = tree(depth - 1)
  22         r.extend([t*ltrafo for t in subtree])
  23         r.extend([t*ctrafo for t in subtree])
  24         r.extend([t*rtrafo for t in subtree])
  25     return r
  26
  27 c = canvas.canvas()
  28 for t in tree(7):
  29     # apply the transformation to a "sub"-canvas and insert it into the "main" canvas
  30     c.insert(canvas.canvas(t).stroke(path.line(0, 0, 0, l)))
  31 c.writetofile("tree", paperformat="a4")
  32