barnsley-fern-makevideo.py

import random
from subprocess import Popen, PIPE

frames, width, height = 120, 720, 720
ppm_header = bytes("P6\n{} {}\n255\n".format(width, height), "ascii")

ff = ['ffmpeg', '-y', '-f', 'image2pipe', '-vcodec', 'ppm', '-r', '24',
      '-i', '-', '-pix_fmt', 'yuv420p', 'barnsley-vid.mp4']
pipe = Popen(ff, stdin=PIPE)

for frame in range(frames):

    pixels = [0] * (width * height)
    x, y = 0, 1
    grow = (1 - (frame/frames - 1) ** 4) * 0.85

    for n in range(60 * width * height):

        r = random.random() * 100
        xn, yn = x, y
        if r < 1:
            x = 0
            y = 0.16 * yn
        elif r < 86:
            x = grow * xn + 0.04 * yn
            y = -0.04 * xn + 0.85 * yn + 1.6
        elif r < 93:
            x = 0.20 * xn - 0.26 * yn
            y = 0.23 * xn + 0.22 * yn + 1.6
        else:
            x = -0.15 * xn + 0.28 * yn
            y = 0.26 * xn + 0.24 * yn + 0.44

        x_pix = int(width * (0.45 + 0.195 * x))
        y_pix = int(height * (1 - 0.099 * y ))
        pixels[x_pix + y_pix * width] += 1

    greys = [max(0, (256 - p) / 256) for p in pixels]
    colors = [int(c * 255) for g in greys for c in [g ** 6, g, g ** 6]]
    pipe.stdin.write(ppm_header + bytes(colors))

pipe.stdin.close()
pipe.wait()