# cbezier6.rb

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

    require 'RMagick'

    imgl = Magick::ImageList.new
    imgl.new_image(400, 300, Magick::HatchFill.new('white','lightcyan2'))

    gc = Magick::Draw.new

    # Draw Bezier curve
    gc.stroke('red')
    gc.stroke_width(2)
    gc.fill_opacity(0)
    gc.bezier(50,150, 50,50, 200,50, 200,150, 200,250, 350,250, 350,150)

    # Draw filled circles for the control points
    gc.fill('gray50')
    gc.stroke('gray50')
    gc.fill_opacity(1)
    gc.circle(50,50, 53,53)
    gc.circle(200,50, 203,53)
    gc.circle(200,250, 203,253)
    gc.circle(350,250, 353,253)

    # Draw circles on the points the curve passes through
    gc.fill_opacity(0)
    gc.circle(50,150, 53,153)
    gc.circle(200,150, 203,153)
    gc.circle(350,150, 353,153)

    # Draw the gray lines between points and control points
    gc.line(50,50, 50,150)
    gc.line(200,50, 200,250)
    gc.line(350,150, 350,250)

    # Annotate
    gc.fill('black')
    gc.stroke('transparent')
    gc.text(30,170, "'50,150'")
    gc.text(30, 40, "'50,50'")
    gc.text(180,40, "'200,50'")
    gc.text(210,155,"'200,150'")
    gc.text(180,270,"'200,250'")
    gc.text(330,270,"'350,250'")
    gc.text(330,140,"'350,150'")
    gc.draw(imgl)

    imgl.border!(1,1, 'lightcyan2')

    imgl.write("cbezier6.gif")
    exit

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