# chop.rb

    #!/usr/bin/ruby1.9.1 -w
    require 'RMagick'

    # Demonstrate the Image#chop method

    img = Magick::Image.read('images/Flower_Hat.jpg')[0]

    # Chop the specified rectangle out of the img.
    chopped = img.chop(0, img.rows/2, img.columns/2, img.rows)

    # Make a "before" image by highlighting the chopped area.
    gc = Magick::Draw.new
    gc.fill('white')
    gc.stroke('transparent')
    gc.fill_opacity(0.25)
    gc.rectangle(0, img.rows/2, img.columns/2, img.rows)
    gc.draw(img)

    img.write('chop_before.jpg')

    # Create a image to use as a background for
    # the after image. Make the chopped image the
    # same size as before the chop.
    bg = Magick::Image.new(img.columns, img.rows)

    chopped = bg.composite(chopped, Magick::NorthEastGravity, Magick::OverCompositeOp)

    chopped.write('chop_after.jpg')
    exit

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