Generate and dump a hexagram in PNG format

hexagram.py

 # -*- coding: utf-8 -*-
 
# Requires PIL (pillow) and NumPy
# Copyright (C) Stephan Hügel, 2016
# License: MIT

import sys
from PIL import Image
import numpy as np

class Hexagram(object):
    """
    Generate and write a hexagram to PNG
    Input is an iterable of six binary digits; 1 is a solid line, 0 a broken line
    Write to hexagram.png by calling .dump()
    
    """
    
    def _black_row(self):
        """ an unbroken bar """
        return np.vstack([
            np.zeros((self.bar_height, 100)),
            np.ones((self.bar_height, 100))]
        )
    
    def _broken_row(self):
        """ a broken bar """
        return np.vstack([
                    np.hstack([
                    np.zeros((self.bar_height, 46)),
                    np.ones((self.bar_height, 8)),
                    np.zeros((self.bar_height, 46))]),
                    np.ones((self.bar_height, 100))]
            )

    def generate(self, pattern):
        """ generate a scaled b&w hexagram """
        container = []
        for digit in self.pattern:
            if digit:
                container.append(self._black_row())
            else:
                container.append(self._broken_row())
        # remove last white row
        container[-1] = container[-1][0:self.bar_height]
        stacked = np.vstack(container)
        # rescale to 256 x 8-bit    
        return (255.0 / stacked.max() * (stacked - stacked.min())).astype(np.uint8)
    
    def dump(self):
        """ write hexagram to PNG """
        im = Image.fromarray(self.generated)
        im.save('hexagram.png')
        
    def __init__(self, pattern):
        self.bar_height = 8
        self.pattern = pattern
        self.generated = self.generate(pattern)