Cut circle out of image with RMagick

Question

I want to cut a circle out of an image using rmagick.

Here's an example of what I'd like to be able to accomplish:

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It seems like I want to use http://studio.imagemagick.org/RMagick/doc/draw.html#circle to cut a circle, and then clip_path to mask it, but the docs aren't very clear. Would anyone be able to point me in the right direction?

Answer 1

require 'rmagick'

im = Magick::Image.read('walter.jpg').first

circle = Magick::Image.new 200, 200
gc = Magick::Draw.new
gc.fill 'black'
gc.circle 100, 100, 100, 1
gc.draw circle

mask = circle.blur_image(0,1).negate

mask.matte = false
im.matte = true
im.composite!(mask, Magick::CenterGravity, Magick::CopyOpacityCompositeOp)

im.write 'walter_circle.png'