langton.py

import os

from PIL import Image
import numpy as np


width, height = 800, 600
grid = np.zeros((height, width), dtype=np.uint8)

x = y = int(width / 2)
d = 0

imgs = []

for i in range(10):
    for a in range(100000):
        if grid[y, x]:
            d -= 1
        else:
            d += 1
        d %= 4
        #if d < 0: d = 3
        #elif d > 3: d = 0
        
        grid[y, x] = 1 - grid[y, x]
        #print(grid[x, y])

        if d == 0: y -= 1
        elif d == 1: x += 1
        elif d == 2: y += 1
        else: x -= 1

        x %= width
        y %= height
        #if x >= width: x = 0
        #elif x < 0: x = width - 1
        #elif y >= height: y = 0
        #elif y < 0: y = height - 1
        #print(x, y, d)

    ia = ((1 - grid) * 255).repeat(3).reshape(height, width, 3)
    i = Image.fromarray(ia)
    imgs.append(i)

os.chdir(os.path.split(__file__)[0] or '.')
print('Sum is', grid.sum())

imgs[0].save('output.gif', loop=0, save_all=True, append_images=imgs[1:])