voronoi.py

# adapted and annotated from rosettacode
# https://rosettacode.org/wiki/Voronoi_diagram#Python

# pillow library
from PIL import Image
import random
import math

# cells is synonymous with sites
def generate_voronoi_diagram(width, height, num_cells, name):
    # image to use
    image = Image.new("RGB", (width, height))
    imgx, imgy = image.size
    # site points
    nx = []
    ny = []
    # site colors
    nr = []
    ng = []
    nb = []
    # place voronoi points
    for i in range(num_cells):
        nx.append(random.randrange(imgx))
        ny.append(random.randrange(imgy))
        # randomize color of site: blue-ish
        nr.append(random.randrange(25) + 100)
        ng.append(random.randrange(25) + 146)
        nb.append(random.randrange(25) + 219)
    # look at every pixel starting in top left
    for y in range(imgy):
        for x in range(imgx):
            # distance from center to corner initially
            # later set as distance to closest site
            dmin = math.hypot(imgx - 1, imgy - 1)
            # which site to use
            j = -1
            # loop through sites
            for i in range(num_cells):
                # find distance to current site
                d = math.hypot(nx[i] - x, ny[i] - y)
                # check if current site is closer
                if d < dmin:
                    dmin = d
                    j = i
            # set current pixel to color of closest cell
            image.putpixel((x, y), (nr[j], ng[j], nb[j]))
    # save image
    image.save(name, "PNG")

# generate diagram
generate_voronoi_diagram(1860, 1920, 32, "screen.png")