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L-system
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from math import sin, cos, radians | |
import cairo | |
import random | |
import re | |
class System(object): | |
def __init__(self, rules): | |
self.rules = rules | |
self.pattern = re.compile('|'.join('(%s)' % x for x in rules)) | |
def step(self, value): | |
def func(match): | |
rule = self.rules[match.group(0)] | |
if isinstance(rule, basestring): | |
return rule | |
return random.choice(rule) | |
return self.pattern.sub(func, value) | |
def run(self, start, iterations): | |
result = [start] | |
for i in range(iterations): | |
result.append(self.step(result[-1])) | |
return result | |
def run(program, dc): | |
angle = radians(25) | |
state = (0.0, 0.0, -radians(45)) | |
stack = [] | |
minx = maxx = miny = maxy = 0 | |
for instruction in program: | |
x, y, a = state | |
if instruction == 'F': | |
x += cos(a) | |
y += sin(a) | |
if dc: | |
dc.line_to(x, y) | |
dc.stroke() | |
dc.move_to(x, y) | |
elif instruction == '-': | |
a -= angle | |
elif instruction == '+': | |
a += angle | |
elif instruction == '[': | |
stack.append(state) | |
elif instruction == ']': | |
x, y, a = stack.pop() | |
if dc: | |
dc.move_to(x, y) | |
state = (x, y, a) | |
minx = min(minx, x) | |
miny = min(miny, y) | |
maxx = max(maxx, x) | |
maxy = max(maxy, y) | |
return (minx, miny, maxx, maxy) | |
def render(program): | |
size = 1024 | |
pad = 40 | |
minx, miny, maxx, maxy = run(program, None) | |
width, height = size, size * ((maxy - miny) / (maxx - minx)) | |
width, height = int(width + pad), int(height + pad) | |
scale = size / (maxx - minx) | |
surface = cairo.ImageSurface(cairo.FORMAT_RGB24, width, height) | |
dc = cairo.Context(surface) | |
dc.set_line_cap(cairo.LINE_CAP_ROUND) | |
# dc.set_line_width(3) | |
dc.set_source_rgba(0, 0, 0, 1) | |
dc.paint() | |
dc.translate(pad / 2, pad / 2) | |
dc.scale(scale, scale) | |
dc.translate(-minx, -miny) | |
dc.set_source_rgba(1, 1, 1, 0.1) | |
dc.move_to(0, 0) | |
run(program, dc) | |
surface.write_to_png('output.png') | |
def main(): | |
system = System({ | |
'X': 'F-[[X]+X]+F[+FX]-X', | |
'F': 'FF', | |
}) | |
program = system.run('X', 9)[-1] | |
render(program) | |
if __name__ == '__main__': | |
main() |
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