pudding.py

from __future__ import annotations
from PIL import Image
import numpy as np


def ease_in_out_quad(t):
    return t * t * (3.0 - 2.0 * t)


def find_coeffs(pa, pb):
    matrix = []
    for p1, p2 in zip(pa, pb):
        matrix.append([p1[0], p1[1], 1, 0, 0, 0, -p2[0] * p1[0], -p2[0] * p1[1]])
        matrix.append([0, 0, 0, p1[0], p1[1], 1, -p2[1] * p1[0], -p2[1] * p1[1]])

    A = np.matrix(matrix, dtype=np.float64)
    B = np.array(pb).reshape(8)

    res = np.dot(np.linalg.inv(A.T * A) * A.T, B)
    return np.array(res).reshape(8)


def transform(startpoints, endpoints, im):
    width, height = im.size
    coeffs = find_coeffs(endpoints, startpoints)

    im = im.transform((width, height), Image.PERSPECTIVE, coeffs, Image.BICUBIC, fillcolor=(0, 0, 0, 0))
    return im


def transition(start, stop, t: float):
    start = np.array(start)
    stop = np.array(stop)
    return start + (stop - start) * ease_in_out_quad(t)


def main():
    im = Image.open('pudding-original.webp')
    im = im.convert('RGBA')

    bg = Image.new('RGBA', im.size, (0, 0, 0, 0))
    bg.paste(im, mask=im)
    im = bg

    width, height = im.size

    positions = {
        'normal': [(0, 0), (width, 0), (width, height), (0, height)],
        'flat': [(0, height * 0.2), (width, height * 0.2), (width, height), (0, height)],
        'flat-wide': [(-width * 0.1, height * 0.3), (width + width * 0.1, height * 0.3), (width, height), (0, height)],
        'right': [(width * 0.3, 0), (width + width * 0.05, 0), (width, height), (0, height)],
        'left': [(-width * 0.05, 0), (width - width * 0.3, 0), (width, height), (0, height)],
    }

    frames = []

    steps = [
        ('flat', 4),
        ('flat-wide', 3),
        ('left', 5),
        ('flat', 4),
        ('flat-wide', 3),
        ('right', 5),
        ('flat', 4),
    ]

    total_time = sum(step[1] for step in steps)
    nb_frames = 50

    acc_steps = []
    acc = 0
    for name, weight in steps:
        acc += weight
        acc_steps.append((name, acc / total_time))

    print(f'{width=}\n{height=}')
    print()

    for key, position in positions.items():
        print(f'{key:>10}:', [f'{v[0]:7.3f}, {v[1]:7.3f}' for v in position])

    base_step = acc_steps[0][1]
    # adjust steps to start at 0 but keep the last one at 1.0
    range_values = 1.0 - base_step
    acc_steps = [(a, (t - base_step) / range_values) for a, t in acc_steps]

    print()
    print(*acc_steps, sep='\n')
    print()

    for i in range(nb_frames):
        t = i / nb_frames
        for (a1, t_step1), (a2, t_step2) in zip(acc_steps, acc_steps[1:]):
            if t_step1 <= t <= t_step2:
                ratio = (t - t_step1) / (t_step2 - t_step1)
                values = transition(positions[a1], positions[a2], ratio)
                frame = transform(positions['normal'], values, im)
                frames.append(frame)
                print(
                    f'{a1:<10} {a2:<10} {ratio=:.4f}  {t_step1=:.3f} {t_step2=:.3f}  ',
                    [f'{v[0]:7.3f}, {v[1]:7.3f}' for v in values]
                )
                break

    print({f.size for f in frames})

    frames[0].save('pudding.gif', save_all=True, append_images=frames[1:], duration=20, loop=0, disposal=2)


if __name__ == '__main__':
    main()