cropping an image in a circular way, using python

Question

I want to create a script that crops an image in a circular way.

I have a server which receives all kind of pictures (all of the same size) and I want the server to crop the received image.

For example, turn this image:

into this:

I want to be able to save it as a PNG (with a transparent background).

How can this be done?

There aren't even real concrete requirements here, much less a specific question of any kind. — Mad Physicist, Jul 23 '18 at 19:54
Use Pillow to draw a white circle on a black bakground and add it as an extra channel, then save. — Mark Setchell, Jul 23 '18 at 20:00
it is not cropping, it is basically masking. You can make a circular mask and use it as an alpha channel. — user8190410, Jul 23 '18 at 20:26

score 16 · Accepted Answer · answered Jul 23 '18 at 21:01

Here's one way to do it:

#!/usr/local/bin/python3
import numpy as np
from PIL import Image, ImageDraw

# Open the input image as numpy array, convert to RGB
img=Image.open("dog.jpg").convert("RGB")
npImage=np.array(img)
h,w=img.size

# Create same size alpha layer with circle
alpha = Image.new('L', img.size,0)
draw = ImageDraw.Draw(alpha)
draw.pieslice([0,0,h,w],0,360,fill=255)

# Convert alpha Image to numpy array
npAlpha=np.array(alpha)

# Add alpha layer to RGB
npImage=np.dstack((npImage,npAlpha))

# Save with alpha
Image.fromarray(npImage).save('result.png')

cropping an image in a circular way, using python

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