# qbezierpath.rb

    #!/usr/local/bin/ruby19 -w
    require 'RMagick'

    imgl = Magick::ImageList.new
    imgl.new_image(500, 300, Magick::HatchFill.new('white','lightcyan2'))

    gc = Magick::Draw.new

    # Draw path with quadratic bezier commands
    gc.fill_opacity 0
    gc.stroke 'red'
    gc.stroke_width 3
    gc.path "M20,150 Q120,25 220,150 T420,150"

    # Annotate
    # Show end points
    gc.fill_opacity 1
    gc.stroke 'grey50'
    gc.stroke_width 1
    gc.circle 20,150,   23, 153
    gc.circle 220,150, 223, 153
    gc.circle 420,150, 423, 153

    # Show control points
    gc.fill 'black'
    gc.stroke 'transparent'
    gc.circle 120,25,  123, 28
    gc.circle 320,275, 323, 278

    # Show connector lines
    gc.line  20,150, 120,25
    gc.line 120,25,  320,275
    gc.line 320,275, 420,150

    # Add labels
    gc.font_weight Magick::NormalWeight
    gc.font_style Magick::NormalStyle

    # Add end point labels
    gc.text  30,155, "'20,150'"
    gc.text 230,155, "'220,150'"
    gc.text 430,155, "'420,150'"

    # Add control point labels
    gc.text 130,30, "'120,25'"
    gc.text 330,280, "'320,275'"

    gc.draw imgl

    imgl.border!(1,1, "lightcyan2")
    #imgl.display
    imgl.write "qbezierpath.gif"

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