python 给图像添加透明度(alpha通道)

#-*- coding: UTF-8 -*- 
 
from PIL import Image
 
def addTransparency(img, factor = 0.7 ):
  img = img.convert('RGBA')
  img_blender = Image.new('RGBA', img.size, (0,0,0,0))
  img = Image.blend(img_blender, img, factor)
  return img
 
 
img = Image.open( "SMILEY.png ")
img = addTransparency(img, factor =0.7)

#-*- coding: UTF-8 -*- 
 
from PIL import Image
 
img = Image.open("SMILEY.png ")
img = img.convert('RGBA')
r, g, b, alpha = img.split()
alpha = alpha.point(lambda i: i>0 and 178)
img.putalpha(alpha)