examples/tree.py

   1 # fractal tree
   2 # contributed by Gerhard Schmid and André Wobst
   3
   4 from pyx import *
   5
   6 # base tree length
   7 l = 5
   8
   9 # base transformations for the left, center, and right part of the tree
  10 ltrafo = trafo.rotate(65).scaled(0.4).translated(0, l * 2.0 / 3.0)
  11 ctrafo = trafo.rotate(-4).scaled(0.75).translated(0, l)
  12 rtrafo = trafo.mirror(90).rotated(-65).scaled(0.35).translated(0, l)
  13
  14 def tree(depth):
  15     "return transformations for a recursive tree of given depth"
  16     r = [trafo.rotate(5)]
  17     if depth > 0:
  18         subtree = tree(depth - 1)
  19         r.extend([t*ltrafo for t in subtree])
  20         r.extend([t*ctrafo for t in subtree])
  21         r.extend([t*rtrafo for t in subtree])
  22     return r
  23
  24 c = canvas.canvas()
  25 for t in tree(7):
  26     # apply the transformation to a "sub"-canvas and insert it into the "main" canvas
  27     c.insert(canvas.canvas(t).stroke(path.line(0, 0, 0, l)))
  28 c.writetofile("tree", paperformat="a4")
  29