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如何用Python画各种著名数学图案 | 附图+代码

中科院物理所 · 公众号 · 物理 · 2017-04-26 10:21

正文

本文经授权转自微信公众号“大数据文摘 | bigdatadigest”

编译团队：Aileen，徐凌霄

用Python绘制著名的数学图片或动画，

展示数学中的算法魅力。

Mandelbrot 集

代码：46 lines (34 sloc) 1.01 KB

	'''
	A fast Mandelbrot set wallpaper renderer

	reddit discussion: https://www.reddit.com/r/math/comments/2abwyt/smooth_colour_mandelbrot/
	'''
	import numpy as np
	from PIL import Image
	from numba import jit


	MAXITERS = 200
	RADIUS = 100


	@jit
	def color(z, i):
	v = np.log2(i + 1 - np.log2(np.log2(abs(z)))) / 5
	if v < 1.0:
	return v4, v2.5, v
	else:
	v = max(0, 2-v)
	return v, v1.5, v3


	@jit
	def iterate(c):
	z = 0j
	for i in range(MAXITERS):
	if z.realz.real + z.imagz.imag > RADIUS:
	return color(z, i)
	z = z*z + c
	return 0, 0 ,0


	def main(xmin, xmax, ymin, ymax, width, height):
	x = np.linspace(xmin, xmax, width)
	y = np.linspace(ymax, ymin, height)
	z = x[None, :] + y[:, None]*1j
	red, green, blue = np.asarray(np.frompyfunc(iterate, 1, 3)(z)).astype(np.float)
	img = np.dstack((red, green, blue))
	Image.fromarray(np.uint8(img*255)).save('mandelbrot.png')


	if __name__ == '__main__':
	main(-2.1, 0.8, -1.16, 1.16, 1200, 960)

多米诺洗牌算法

代码链接：https://github.com/neozhaoliang/pywonderland/tree/master/src/domino

正二十面体万花筒

代码：53 lines (40 sloc) 1.24 KB

	'''
	A kaleidoscope pattern with icosahedral symmetry.
	'''
	import numpy as np
	from PIL import Image
	from matplotlib.colors import hsv_to_rgb


	def Klein(z):
	'''Klein's j-function'''
	return 1728 * (z * (z*10 + 11 z5 - 1))5 / \
	(-(z*20 + 1) + 228 (z15 - z5) - 494 * z10)3


	def RiemannSphere(z):
	'''
	map the complex plane to Riemann's sphere via stereographic projection
	'''
	t = 1 + z.realz.real + z.imagz.imag
	return 2z.real/t, 2z.imag/t, 2/t-1


	def Mobius(z):
	'''
	distort the result image by a mobius transformation
	'''
	return (z - 20)/(3*z + 1j)


	def main(imgsize):
	x = np.linspace(-6, 6, imgsize)
	y = np.linspace(6, -6, imgsize)
	z = x[None, :] + y[:, None]*1j
	z = RiemannSphere(Klein(Mobius(Klein(z))))

	# define colors in hsv space
	H = np.sin(z[0]np.pi)*2
	S = np.cos(z[1]np.pi)*2
	V = abs(np.sin(z[2]np.pi) np.cos(z[2]np.pi))*0.2
	HSV = np.dstack((H, S, V))

	# transform to rgb space
	img = hsv_to_rgb(HSV)
	Image.fromarray(np.uint8(img*255)).save('kaleidoscope.png')


	if __name__ == '__main__':
	import time
	start = time.time()
	main(imgsize=800)
	end = time.time()
	print('runtime: {:3f} seconds'.format(end - start))

Newton 迭代分形

代码：46 lines (35 sloc) 1.05 KB

	import numpy as np
	import matplotlib.pyplot as plt
	from numba import jit


	# define functions manually, do not use numpy's poly1d funciton!
	@jit('complex64(complex64)', nopython=True)
	def f(z):
	# zzz is faster than z**3
	return zzz - 1


	@jit('complex64(complex64)', nopython=True)
	def df(z):
	return 3zz


	@jit('float64(complex64)', nopython=True)
	def iterate(z):
	num = 0
	while abs(f(z)) > 1e-4:
	w = z - f(z)/df(z)
	num += np.exp(-1/abs(w-z))
	z = w
	return num


	def render(imgsize):
	x = np.linspace(-1, 1, imgsize)
	y = np.linspace(1, -1, imgsize)
	z = x[None, :] + y[:, None] * 1j
	img = np.frompyfunc(iterate, 1, 1)(z).astype(np.float)
	fig = plt.figure(figsize=(imgsize/100.0, imgsize/100.0), dpi=100)
	ax = fig.add_axes([0, 0, 1, 1], aspect=1)
	ax.axis('off')
	ax.imshow(img, cmap='hot')
	fig.savefig('newton.png')


	if __name__ == '__main__':
	import time
	start = time.time()
	render(imgsize=400)
	end = time.time()
	print('runtime: {:03f} seconds'.format(end - start))

李代数E8 的根系

代码链接：https://github.com/neozhaoliang/pywonderland/blob/master/src/misc/e8.py

模群的基本域

代码链接：

https://github.com/neozhaoliang/pywonderland/blob/master/src/misc/modulargroup.py

彭罗斯铺砌

代码链接：

https://github.com/neozhaoliang/pywonderland/blob/master/src/misc/penrose.py

Wilson 算法

代码链接：https://github.com/neozhaoliang/pywonderland/tree/master/src/wilson

反应扩散方程模拟

代码链接：https://github.com/neozhaoliang/pywonderland/tree/master/src/grayscott

120 胞腔

代码：69 lines (48 sloc) 2.18 KB

	# pylint: disable=unused-import
	# pylint: disable=undefined-variable

	from itertools import combinations, product
	import numpy as np
	from vapory import *


	class Penrose(object):

	GRIDS = [np.exp(2j * np.pi * i / 5) for i in range(5)]

	def __init__(self, num_lines, shift, thin_color, fat_color, **config):
	self.num_lines = num_lines
	self.shift = shift
	self.thin_color = thin_color
	self.fat_color = fat_color
	self.objs = self.compute_pov_objs(**config)


	def compute_pov_objs(self, **config):
	objects_pool = []

	for rhombi, color in self.tile():
	p1, p2, p3, p4 = rhombi
	polygon = Polygon(5, p1, p2, p3, p4, p1,
	Texture(Pigment('color', color), config['default']))
	objects_pool.append(polygon)

	for p, q in zip(rhombi, [p2, p3, p4, p1]):
	cylinder = Cylinder(p, q, config['edge_thickness'], config['edge_texture'])
	objects_pool.append(cylinder)

	for point in rhombi:
	x, y = point
	sphere = Sphere((x, y, 0), config['vertex_size'], config['vertex_texture'])
	objects_pool.append(sphere)

	return Object(Union(*objects_pool))


	def rhombus(self, r, s, kr, ks):
	if (s - r)**2 % 5 == 1:
	color = self.thin_color
	else:
	color = self.fat_color

	point = (Penrose.GRIDS[r] * (ks - self.shift[s])
	- Penrose.GRIDS[s] * (kr - self.shift[r])) *1j / Penrose.GRIDS[s-r].imag
	index = [np.ceil((point/grid).real + shift)
	for grid, shift in zip(Penrose.GRIDS, self.shift)]

	vertices = []
	for index[r], index[s] in [(kr, ks), (kr+1, ks), (kr+1, ks+1), (kr, ks+1)]:
	vertices.append(np.dot(index, Penrose.GRIDS))

	vertices_real = [(z.real, z.imag) for z in vertices]
	return vertices_real, color


	def tile(self):
	for r, s in combinations(range(5), 2):
	for kr, ks in product(range(-self.num_lines, self.num_lines+1), repeat=2):
	yield self.rhombus(r, s, kr, ks)


	def put_objs(self, *args):
	return Object(self.objs, *args)

原文链接：https://github.com/neozhaoliang/pywonderland/blob/master/README.md

本文经授权转载自大数据文摘

编辑：yangfz

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