program for drawing @Cwillmore banner

draw.py

# 05/02/18 04:46 PM
# program to draw twitter background
# might be a good foundation for beesandbombs-style animation?

from PIL import Image, ImageDraw
import os
import aggdraw
import random
import math

w = 1500
h = 500

def prob_density(x, y):
    return math.exp(5 * x / w)

def sample():
    x = random.uniform(0, w)
    y = random.uniform(0, h)
    score = prob_density(x, y)

    for i in range(200):
        xx = random.uniform(0, w)
        yy = random.uniform(0, h)
        new_score = prob_density(xx, yy)
        should_step = new_score > score or random.uniform(0, 1) < new_score / score
        if should_step:
            x = xx
            y = yy
            score = new_score
    return x, y

gray_bg = '#d5d5d7'
white_dot = '#fbfafb'

identity_transform = (1, 0, 0, 0, 1, 0)
transform_stack = [identity_transform]

def compose(t1, t2):
    a1, b1, c1, d1, e1, f1 = t1
    a2, b2, c2, d2, e2, f2 = t2
    return (
        a1 * a2 + b1 * d2,
        a1 * b2 + b1 * e2,
        a1 * c2 + b1 * f2 + c1,
        d1 * a2 + e1 * d2,
        d1 * b2 + e1 * e2,
        d1 * c2 + e1 * f2 + f1
    )

def append_transform(t):
    transform_stack[-1] = compose(transform_stack[-1], t)
    ctx.settransform(transform_stack[-1])

def translate(dx, dy):
    append_transform((1, 0, dx, 0, 1, dy))

def rotate(theta):
    s = math.sin(theta)
    c = math.cos(theta)
    append_transform((c, -s, 0, s, c, 0))

def scale(s):
    append_transform((s, 0, 0, 0, s, 0))
    # TODO: scale pen size too?

def pushstate():
    transform_stack.append(transform_stack[-1])

def popstate():
    transform_stack.pop()
    ctx.settransform(transform_stack[-1])

img = Image.new("RGBA", (w, h))
ctx = aggdraw.Draw(img)
ctx.rectangle((0, 0, w, h), None, aggdraw.Brush(gray_bg))
num_points = 1000
for i in range(num_points):
    x, y = sample()
    theta = -math.pi/4 + random.normalvariate(0, math.pi/12)
    #theta=math.pi/4
    p = aggdraw.Pen(white_dot, 2)
    pushstate()
    translate(x, y)
    rotate(theta)
    scale(0.6)
    ctx.line((0, 0, 8, 0), p)
    if random.choice((True, False)):
        ctx.line((-6, 10, 2, 10), p)
    popstate()
ctx.flush()
img.save(os.path.expanduser("~/Desktop/out.png"))