Speed up Telegram .tgs stickers, using a lottie precomposition layer

speed.py

import sys
import gzip
import json

if len(sys.argv) < 3:
    print("Wrong args. Usage: python speed.py file.tgs 150%")

sticker = json.load(gzip.open(sys.argv[1]))
stretch = 100 / float(sys.argv[2].strip(" %"))

# https://lottiefiles.github.io/lottie-docs/breakdown/precomps/
# https://lottiefiles.github.io/lottie-docs/layers/#precomposition-layer

sticker["assets"].append(
    {
        "id": "precomp_layer",
        "layers": sticker["layers"]
    }
)

sticker["layers"] = [
    {
        "ty": 0,
        "ip": sticker["ip"] * stretch,
        "op": sticker["op"] * stretch,
        "w": sticker["w"],
        "h": sticker["h"],
        "refId": "precomp_layer",
        "st": 0,
        "sr": stretch,
        "ind": 0,
        "ks": {}
    }
]

sticker["op"] *= stretch

with open(f"speed_output.tgs", "wb") as output_tgs, open("speed_output.json", "w") as output_json:
    json.dump(sticker, output_json, indent=2)
    jsoned = json.dumps(sticker, separators=(',', ':'))
    output_tgs.write(gzip.compress(jsoned.encode()))