# path.rb

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

    imgl = Magick::ImageList.new
    imgl.new_image(390, 240, Magick::HatchFill.new('white','lightcyan2'))

    gc = Magick::Draw.new

    # Draw path
    gc.fill_opacity 0
    gc.stroke 'red'
    gc.stroke_width 3
    gc.path "M20,120 C20,20 170,20 170,120 S320,220 320,120"

    # Annotate
    # Show end points
    gc.fill_opacity 0
    gc.stroke 'gray50'
    gc.stroke_width 1
    gc.circle  20,120,  23, 123
    gc.circle 170,120, 173, 123
    gc.circle 320,120, 323, 123

    # Show control points
    gc.fill_opacity 1
    gc.circle  20, 20,  23,  23
    gc.circle 170, 20, 173,  23
    gc.circle 320,220, 323, 223

    # Show connector lines
    gc.line  20,120,  20, 20
    gc.line 170, 20, 170,220
    gc.line 320,220, 320,120

    # Show auto control point
    gc.fill_opacity 0
    gc.stroke 'blue'
    gc.stroke_width 3
    gc.circle 170,220, 173,223

    # Add labels
    gc.stroke "#000000ff"       # unset stroke color
    gc.fill 'black'

    # Add end point labels
    gc.text  30,125, "'20,120'"
    gc.text 180,125, "'170,120'"
    gc.text 330,125, "'320,120'"

    # Add control point labels
    gc.text  30, 25, "'20,20'"
    gc.text 180, 25, "'170,20'"
    gc.text 330,225, "'320,320'"

    # Add auto control point label
    gc.text 180,225, "'auto ctl point'"

    gc.draw imgl

    imgl.border!(1,1, 'lightcyan2')
    imgl.write 'path.gif'

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