如何利用python给图片添加半透明水印

# coding:utf-8

from PIL import Image, ImageDraw, ImageFont


def add_text_to_image(image, text):
 font = ImageFont.truetype('C:\Windows\Fonts\STXINGKA.TTF', 36)

 # 添加背景
 new_img = Image.new('RGBA', (image.size[0] * 3, image.size[1] * 3), (0, 0, 0, 0))
 new_img.paste(image, image.size)

 # 添加水印
 font_len = len(text)
 rgba_image = new_img.convert('RGBA')
 text_overlay = Image.new('RGBA', rgba_image.size, (255, 255, 255, 0))
 image_draw = ImageDraw.Draw(text_overlay)

 for i in range(0, rgba_image.size[0], font_len*40+100):
  for j in range(0, rgba_image.size[1], 200):
   image_draw.text((i, j), text, font=font, fill=(0, 0, 0, 50))
 text_overlay = text_overlay.rotate(-45)
 image_with_text = Image.alpha_composite(rgba_image, text_overlay)

 # 裁切图片
 image_with_text = image_with_text.crop((image.size[0], image.size[1], image.size[0] * 2, image.size[1] * 2))
 return image_with_text


if __name__ == '__main__':
 img = Image.open("test.jpg")
 im_after = add_text_to_image(img, u'测试使用')
 im_after.save(u'测试使用.png')