    #! /usr/local/bin/ruby -w
    require 'RMagick'

    # Demonstrate the Image#gaussian_blur method

    lighthouse = Magick::Image.read('images/Lighthouse.jpg').first

    # Crop to the interesting part of the picture.
    lighthouse = lighthouse.crop(202, 184, 206, 230)

    # Make a blurry copy
    blurry = lighthouse.gaussian_blur(0.0, 3.0)

    # Copy the copy, retaining only the right half.
    blurry = blurry.crop(blurry.columns/2, 0, blurry.columns/2, blurry.rows)

    # Composite the copy over the right half of the original.
    result = lighthouse.composite(blurry, Magick::EastGravity, Magick::OverCompositeOp)

    # Draw a black line between the before and after parts.
    line = Magick::Draw.new
    line.stroke('white')
    line.line(lighthouse.columns/2, 0, lighthouse.columns/2, lighthouse.rows)
    line.draw(result)

    #result.display
    result.write('gaussian_blur.jpg')
    exit