lsca.uni.py

#!/usr/bin/env python3

import sys
import numpy as np


def lament(*args, **kwargs):
    return print(*args, file=sys.stderr, **kwargs)


def colorize(x):
    return x * 17 % 256


def render(row, scale):
    grays = colorize(row)
    if scale > 1:
        grays = np.repeat(grays, scale)
    line = " ".join(str(x) for x in grays)
    for y in range(scale):
        print(line)


def limit(row):  # in-place
    row[row < 0] = 0
    row[row > 15] = 15
    return row


def initialize(width):
    row = np.zeros(width, int)
    value = 0
    for i in range(width):
        if np.random.randint(8) == 0:  # only change values occasionally
            value = np.random.randint(16)
        row[i] = value
    limit(row)
    return row


name, args = sys.argv[0], sys.argv[1:]

if len(args) == 0:
    rule_lut = None
elif len(args) == 16:
    rule_lut = [int(x.strip(",")) for x in args]
else:
    lament(f"usage: {name}")
    lament(f"usage: {name} {{rules 1 through 16}}")
    sys.exit(1)

scale = 3
width, height = 960 // scale, 960 // scale

if rule_lut is None:
    rule_lut = np.random.randint(-2, 2 + 1, size=(4, 4))
    lament(" ".join(f"{x:+2}" for x in rule_lut.flat))
else:
    rule_lut = np.array(rule_lut).reshape(4, 4)

print("P2")  # magic code for an ascii Portable GrayMap (PGM) file
print(width * scale, height * scale)
print(255)  # maximum color value

row = initialize(width)

for i in range(height):
    # left, center, right:
    L = np.roll(row, 1)
    C = row.copy()
    R = np.roll(row, -1)

    diffusion = (L + C + C + R + 2) // 4

    # v = [0,1,2,3,1,0,3,2,2,3,0,1,3,2,1,0][V]
    y = (L ^ (L >> 2)) % 4
    x = (R ^ (R >> 2)) % 4

    delta = rule_lut[y, x]
    row = diffusion + delta

    limit(row)
    render(row, scale)