# channel.rb

    #!/usr/local/bin/ruby18 -w

    require 'RMagick'
    include Magick

    img = Image.read('images/Flower_Hat.jpg').first
    imgs = ImageList.new

    imgs << img
    imgs << img.channel(RedChannel)
    imgs.cur_image['Label'] = 'RedChannel'
    imgs <<  img.channel(GreenChannel)
    imgs.cur_image['Label'] = 'GreenChannel'
    imgs << img.channel(BlueChannel)
    imgs.cur_image['Label'] = 'BlueChannel'

    result = imgs.montage {
        self.tile = "2x2"
        self.background_color = 'black'
        self.stroke = 'transparent'
        self.fill = 'white'
        self.geometry = Geometry.new(img.columns/2, img.rows/2, 5, 5)
        }

    result.write('channel.jpg')

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