Python: resize image to specified file size

resize-image.py

from io import BytesIO
from pathlib import Path

from PIL import Image


def resize_image(image_path: Path, max_size: int=3*1024*1024):
    if image_path.stat().st_size <= max_size:
        return image_path.read_bytes()
    img = Image.open(image_path)
    if img.format != 'PNG':
        with BytesIO() as tmp_io:
            img.save(tmp_io, format=img.format, quality=90, optimize=True)
            if tmp_io.tell() <= max_size:
                return tmp_io.getvalue()
    new_img_value = None
    width, height = img.size
    l = 100
    r = int(height / 10) + 1
    # print(f'original size: {width, height}')
    # print(f'file size: {image_path.stat().st_size/1024/1024:.2f}MB')
    while l < r:
        m = int((l + r) / 2)
        new_height = m*10
        new_width = round(new_height / height * width)
        new_img = img.resize((new_width, new_height), Image.LANCZOS)
        with BytesIO() as tmp_io:
            new_img.save(tmp_io, format=img.format, quality=90, optimize=True)
            new_file_size = tmp_io.tell()
            new_img_value = tmp_io.getvalue()
        # print(f'new size: {new_width, new_height}')
        # print(f'file size: {new_file_size/1024/1024:.2f}MB')
        if abs(new_file_size - max_size) < 0.2*1024*1024:
            break
        if new_file_size < max_size:
            l = m + 1
        else:
            r = m
    return new_img_value