https://blog.csdn.net/qq_25013919/article/details/79740536
from PIL import Image
def save_image(input_name, output_name):
im = Image.open(input_name)
if im.mode=="RGBA":
im.load() # required for png.split()
background = Image.new("RGB", im.size, (255, 255, 255))
background.paste(im, mask=im.split()[3]) # 3 is the alpha channel
im = background
im.save('{}.jpg'.format(output_name),'JPEG')
