# opacity.rb

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

    require 'RMagick'
    include Magick

    canvas = Image.new(260, 125)
    gc = Draw.new
    gc.fill('black')
    gc.rectangle(10,20, 250,90)

    gc.stroke('blue')
    gc.fill('yellow')
    gc.stroke_width(10)

    gc.opacity('25%')
    gc.roundrectangle(20,20, 60,90, 5,5)

    gc.opacity('50%')
    gc.roundrectangle(80,20, 120,90, 5,5)

    gc.opacity(0.75)
    gc.roundrectangle(140,20, 180,90, 5,5)

    gc.opacity(1)
    gc.roundrectangle(200,20, 240,90, 5,5)

    gc.stroke('transparent')
    gc.fill('black')
    gc.gravity(SouthGravity)
    gc.text(-90,20, '"25%%"')
    gc.text(-30,20, '"50%%"')
    gc.text( 30,20, '"75%%"')
    gc.text( 90,20, '"100%%"')

    gc.draw(canvas)

    canvas.write("opacity.gif")
    exit

Close window