# cbezier4.rb

    #!/usr/local/bin/ruby18 -w
    require 'RMagick'

    imgl = Magick::ImageList.new
    imgl.new_image(390, 360, Magick::HatchFill.new('white','lightcyan2'))
    gc = Magick::Draw.new

    # Draw Bezier curve
    gc.stroke('red')
    gc.stroke_width(3)
    gc.fill_opacity(0)
    gc.bezier(20,180, 20,30, 320, 330, 320,180)

    # Draw circles around endpoints
    gc.fill_opacity(0)
    gc.stroke('gray50').stroke_width(1)
    gc.circle(20,180, 23, 183)
    gc.circle(320,180, 323, 183)

    # Draw filled circles around control points
    gc.line(20,180, 20,30)
    gc.line(320,180, 320,330)
    gc.fill_opacity(1)
    gc.fill('gray50')
    gc.circle(20,30, 23,33)
    gc.circle(320,330, 323,333)

    # Annotate
    gc.font_weight(Magick::NormalWeight)
    gc.font_style(Magick::NormalStyle)
    gc.fill('black')
    gc.stroke('transparent')
    gc.text(29,180, "'20,180'")
    gc.text(29,33,  "'20,30'")
    gc.text(329,330, "'320,330'")
    gc.text(329,180, "'320,180'")

    gc.draw(imgl)
    imgl.border!(1,1, "lightcyan2")

    imgl.write('cbezier4.gif')
    exit(0)

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