"""Gera o fundo night.jpg do Freaky Towers (substitui a foto do Unsplash): ceu noturno em degrade com nuvens
de ruido, estrelas e uma lua. Obra nossa, dedicada ao dominio publico (CC0 1.0). Usa so o Pillow.
Uso: python make-night.py night.jpg"""
import random
import sys
from PIL import Image, ImageChops, ImageDraw, ImageFilter

W, H = 1125, 2000
random.seed(1307)

# Degrade vertical (azul-noite no alto, roxo escuro embaixo).
grad = Image.linear_gradient("L").resize((W, H))
top, bot = Image.new("RGB", (W, H), (6, 9, 28)), Image.new("RGB", (W, H), (36, 26, 64))
img = Image.composite(bot, top, grad)

# Nuvens: ruido borrado em duas escalas, so os picos viram nuvem.
def cloud_layer(scale, blur, gain):
    n = Image.effect_noise((W // scale, H // scale), 90).filter(ImageFilter.GaussianBlur(blur))
    n = n.resize((W, H), Image.BICUBIC)
    return n.point(lambda v: max(0, min(255, int((v - 128) * gain))))
clouds = ImageChops.add(cloud_layer(8, 3, 3.0), cloud_layer(3, 2, 2.0), scale=2)
tint = Image.new("RGB", (W, H), (96, 96, 140))
img = Image.composite(tint, img, clouds.point(lambda v: v * 40 // 100))

# Estrelas.
d = ImageDraw.Draw(img)
for _ in range(220):
    x, y = random.randrange(W), random.randrange(H)
    c = random.randrange(110, 230)
    r = random.choice((0, 0, 0, 1))
    d.ellipse((x - r, y - r, x + r, y + r), fill=(c, c, min(255, c + 20)))

# Lua com halo.
halo = Image.new("L", (W, H), 0)
ImageDraw.Draw(halo).ellipse((780 - 90, 520 - 90, 780 + 90, 520 + 90), fill=110)
halo = halo.filter(ImageFilter.GaussianBlur(70))
img = Image.composite(Image.new("RGB", (W, H), (120, 130, 190)), img, halo)
d = ImageDraw.Draw(img)
d.ellipse((780 - 60, 520 - 60, 780 + 60, 520 + 60), fill=(232, 232, 220))
d.ellipse((780 - 22, 520 - 20, 780 - 2, 520 + 2), fill=(214, 214, 204))
d.ellipse((780 + 10, 520 + 14, 780 + 34, 520 + 38), fill=(220, 220, 209))

img.save(sys.argv[1], quality=88, optimize=True)