python对图片进行最大边大小缩放

def split_image_bs4(file, max_len=720):
    """
    切割图片
    :param file: 二进制文件
    :param max_len: 最大长度
    :return: bs64
    """
    # f = base64.b64decode(b64)
    # with io.BytesIO(f) as im:
    im = io.BytesIO(file)
    img = Image.open(im)
    w, h = img.size
    # print(w, h)
    v = max(w, h)
    if v > max_len:
        if v == w:
            final_w = max_len
            final_h = h * (max_len/w)
        else:
            final_w = w * (max_len / h)
            final_h = max_len
        # print(final_w)
        final_img = img.resize((int(final_w), int(final_h)), Image.ANTIALIAS)
        # print(type(final_img))
        img_byte = io.BytesIO()
        final_img.save(img_byte, 'png')
        b64 = base64.b64encode(img_byte.getvalue())
        return b64
    else:
        return base64.b64encode(file)