resize_cover_art.py

#!/usr/bin/env python3
from mutagen.mp4 import MP4, MP4Cover
from io import BytesIO
from PIL import Image
import pathlib
import math

files = list(pathlib.Path(".").glob("**/*.m4a"))
for f in files:
    print(f)
    mp4 = MP4(str(f))
    cover = mp4.get("covr")
    if cover:
        im = Image.open(BytesIO(cover[0]))
        skip = True
        if im.format != "JPEG":
            im = im.convert('RGB')
            skip = False
        ratio = im.height / im.width
        if ratio == 1:
            if im.width > 300:
                im = im.resize([300, 300])
                skip = False
        else:
            if im.width > 320:
                im = im.resize([320, math.floor(320*ratio)])
                skip = False

        if skip:
            print("skip")
        else:
            imgb = BytesIO()
            print("{}x{}".format(im.width, im.height))
            im.save(imgb, format="JPEG")
            mp4.tags["covr"] = [MP4Cover(imgb.getvalue())]
            mp4.save()