Build png files for a GIF anime of Langton's ant

langton.py

# -*- coding: utf-8 -*-
# date: 2015/05/28
# author: @taki__taki__

# packages
import numpy as np
import matplotlib.pyplot as plt

# direction (N=0, E=1, S=2, W=3)
class Direction(object):
	def __init__(self, d):
		self.d = d
	def turn_right(self): self.d = (self.d + 1) % 4
	def turn_left(self):  self.d = (self.d - 1) % 4
	def __str__(self):
		if self.d == 0: return "N"
		elif self.d == 1: return "E"
		elif self.d == 2: return "S"
		elif self.d == 3: return "W"
		else: return "X"

def get_next(x, y, direction):
	if direction.d == 0:   return (x, y+1)
	elif direction.d == 1: return (x+1, y)
	elif direction.d == 2: return (x, y-1)
	elif direction.d == 3: return (x-1, y)
	else: return (x, y)

if __name__ == '__main__':
	# parameters
	X, Y, x0, y0 = 100, 100, 50, 50
	max_iter = 50000

	# initialize the board
	board = np.zeros((X, Y), dtype=np.bool)
	direction = Direction(0)
	
	# iteration (png)
	x, y = x0, y0
	for i in range(max_iter):
		print(i, x, y)
		if x >= X or y >= Y or x < 0 or y < 0: break # out of the board

		# Black: turn right / White: turn left
		if board[x][y]: direction.turn_right()
		else: direction.turn_left()
		board[x][y] = not board[x][y]     # flip
		x, y = get_next(x, y, direction)  # move 1 step

		plt.figure(figsize=(3,3))
		plt.imshow(board, interpolation='nearest', cmap='Greys')
		plt.savefig("pngtmp/png_%05d" % i)
		plt.close()