一、          代码：

from PIL import Image

import math

flag_img = Image.open('guoqi.png').convert("RGBA")

photo_img = Image.open('头像.jpg')

# 国旗图片的宽和高

flag_width, flag_height = flag_img.size

# 截出国旗左上角五角星

crop_flag = flag_img.crop((66, 0, flag_height+66, flag_height))

# 渐变处理

for i in range(flag_height):

    for j in range(flag_height):

            color = crop_flag.getpixel((i, j))

            distance = int(math.sqrt(i*i + j*j))

            alpha = 255 - int(distance//3.5)

            new_color = (*color[:-1], alpha if alpha > 0 else 0)

            crop_flag.putpixel((i, j), new_color)

# 重置图像尺寸

new_crop_flag = crop_flag.resize(photo_img.size)

photo_img.paste(new_crop_flag, (0, 0), new_crop_flag)

# 保存自己的国旗头像

photo_img.save('半透明国旗头像.png')

二、          效果：