Feathered edges on image with Pillow

Question

I\'m trying to figure out how to feather the edges of an image using Pillow with Python.

I need something like this cute cat (ignore the visible edges):

Answer 1

Providing modified solution with gradient paste mask (as requested by @Crickets).

from PIL import Image
from PIL import ImageDraw
from PIL import ImageFilter

RADIUS = 10

# Open an image
im = Image.open(INPUT_IMAGE_FILENAME)

# Paste image on white background
diam = 2*RADIUS
back = Image.new('RGB', (im.size[0]+diam, im.size[1]+diam), (255,255,255))
back.paste(im, (RADIUS, RADIUS))

# Create paste mask
mask = Image.new('L', back.size, 0)
draw = ImageDraw.Draw(mask)
x0, y0 = 0, 0
x1, y1 = back.size
for d in range(diam+RADIUS):
    x1, y1 = x1-1, y1-1
    alpha = 255 if d

Paste mask:

Result: