# matte_floodfill.rb

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

    require 'RMagick'
    include Magick

    img = Image.new(200,200)
    img.compression = LZWCompression

    bg = Image.read('plasma:fractal') {
        self.size = '200x200'
        }

    gc = Draw.new
    gc.stroke_width(2)
    gc.stroke('black')
    gc.fill('white')
    gc.roundrectangle(0, 0, 199, 199, 8, 8)

    gc.fill('yellow')
    gc.stroke('red')
    gc.circle(100, 100, 100,  25)
    gc.draw(img)

    img.write('matte_floodfill_before.gif')

    img.fuzz = 100
    img = img.matte_floodfill(100, 100)

    # Composite the image over a nice bright background
    # so that the transparent pixels will be obvious.
    img = bg[0].composite(img, CenterGravity, OverCompositeOp)

    img.write('matte_floodfill_after.gif')
    exit

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