Apply Knuth/Dockrey glitch function to BadApple

glitched-apple.py

#!/usr/bin/env python

from itertools import chain, repeat

import numpy as np
from PIL import Image, ImageSequence


GIF_PATH = 'Bad.Apple!!.full.2116173.gif'
FRAME_COUNT = 3110

# BadApple is 20 frames/second.  We can output a 20 FPS image sequence
# or we can repeat the BadApple frames and run the glitch at 60 FPS.
EMIT_60FPS = True

# If you only glitch 25% of the pixels, the video is easier to make out.
GLITCH_25 = True

# Matthew Dockrey's version of this
# https://clacks.link/@attoparsec/115590622107796156
# has X and Y reversed, decrements X offset
MIMIC_DOCKREY = True

SCROLL_VERTICALLY = MIMIC_DOCKREY
DECREMENT_OFFSET = MIMIC_DOCKREY

# very small t values are less interesting
MIN_T = 350

# At 20 FPS, animate the glitch faster
T_STEP_20FPS = 3
T_STEP_60FPS = 1


# Knuth's bitwise fractal (AoCP vol 4A)
# (((x ^ ~y) & ((x - 350) >> 3))**2 >> 12) & 1

def glitch(w, h, t):
    x = np.arange(w)
    y = np.arange(h)
    if SCROLL_VERTICALLY:
        l, r = y, ~x
        o = y[:, np.newaxis]    # reshape as column so broadcast will work
    else:
        l, r = ~y, x
        o = x
    m = 3 if GLITCH_25 else 1
    bit = ((((np.bitwise_xor.outer(l, r) & (o - t) >> 3))**2 >> 12) & m) == 1
    return bit


def print_array(name, a):
    print(f'{name}: '
          f'shape={a.shape} '
          f'dtype={a.dtype} '
          f'element={a[0, 0]}')


src_seq = ImageSequence.Iterator(Image.open(GIF_PATH))
t_seq = range(MIN_T, MIN_T + FRAME_COUNT, T_STEP_20FPS)

if EMIT_60FPS:
    src_seq = chain.from_iterable(repeat(f, 3) for f in src_seq)
    t_seq = range(MIN_T, MIN_T + 3 * FRAME_COUNT, T_STEP_60FPS)

if DECREMENT_OFFSET:
    t_seq = reversed(t_seq)

dst_seq = []

for (t, src_im) in zip(t_seq, src_seq):
    src = np.array(src_im)
    bit = glitch(*src_im.size, t)

    if src.shape[2:] == ():
        # one color channel
        mask = bit
    elif src.shape[2:] == (4, ):
        # four color channels
        alpha = np.ones(bit.shape, dtype=bit.dtype)
        mask = np.stack(3 * (bit, ) + (alpha, ), axis=-1)
    else:
        raise NotImplementedError(f'unexpected pixel shape {i=} {src.shape=}')

    dst = src * ~mask + (255 - src) * mask
    dst_im = Image.fromarray(dst)
    dst_seq.append(dst_im)

dst_seq[0].save(
    'test.png',
    save_all=True,
    append_images=dst_seq[1:],
    duration=(1000 / 60 if EMIT_60FPS else 1000 / 20),
    loop=0
)


# Follow this with
#   ffmpeg -i test.png -pix_fmt yuv420p output.mp4