Slackの透過絵文字に白背景をつけます

slack-dark-mode-emoji.py

import os
import requests
from io import BytesIO
from PIL import Image
import numpy as np

TOKEN = os.environ['SLACK_TOKEN']

res = requests.get('https://slack.com/api/emoji.list',
                   headers={'Authorization': f'Bearer {TOKEN}'})
emojis = res.json()['emoji']

for name, url in emojis.items():
    if not url.startswith('https://'):
        continue
    img_bytes = requests.get(url).content
    img = Image.open(BytesIO(img_bytes))
    img_arr = np.asarray(img)
    if len(img_arr.shape) < 3 or img_arr.shape[2] != 4:
        continue
    transparent = img_arr[:, :, 3].min() == 0
    gray = img_arr[:, :, :3].max(axis=2).astype(float)
    gray *= (img_arr[:, :, 3] / 255)
    dark = np.percentile(gray[img_arr[:, :, 3] > 0], 80) <= 80
    if not dark or not transparent:
        continue
    img.save(f'backup/{name}.png')

    white = Image.fromarray(np.ones(img_arr.shape, dtype=img_arr.dtype) * 255)
    white.paste(img, (0, 0), img.split()[3])
    white.save(f'result/{name}.png')