Python中用PIL裁剪或填充图片

from PIL import Image

img = Image.open('lena.jpg')

longer_side = max(img.size)
horizontal_padding = (longer_side - img.size[0]) / 2
vertical_padding = (longer_side - img.size[1]) / 2
img2 = img.crop(
    (
        -horizontal_padding,
        -vertical_padding,
        img.size[0] + horizontal_padding,
        img.size[1] + vertical_padding
    )
)
img2.save("lena2.jpg")

原图：

填充后：