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

    # Demonstrate the Image#opaque method.

    Rows = 100
    Cols = 425

    # Create a solid black image
    ex = Magick::Image.new(Cols, Rows) { self.background_color = 'black' }

    # Annotate with "RMagick"
    text = Magick::Draw.new
    text.annotate(ex, 0,0,0,0, 'RMagick') {
        self.gravity = Magick::CenterGravity
        self.pointsize = 70
        self.font_weight = Magick::BoldWeight
        self.fill = 'gray50'
        self.stroke = 'gray50'
    }

    ex2 = ex.opaque('gray50','MediumOrchid')
    ex2 = ex2.crop(ex2.columns/2, 0, ex2.columns/2, ex2.rows)

    # Composite the foreground over the background.
    composite = ex.composite(ex2, Magick::EastGravity, Magick::OverCompositeOp)
    #composite.display
    composite.write('opaque.gif')

    exit