| h
	  (PLFLT, input)            Hue, in degrees on the colour cone (0.0-360.0)
	  l
	  (PLFLT, input)            Lightness, expressed as a fraction of the axis of the colour
            cone (0.0-1.0)
	  s
	  (PLFLT, input)            Saturation, expressed as a fraction of the radius of the
            colour cone (0.0-1.0)
	  p_r
	  (PLFLT *, output)            Pointer to red intensity (0.0-1.0) of the colour
	  p_g
	  (PLFLT *, output)            Pointer to green intensity (0.0-1.0) of the colour
	  p_b
	  (PLFLT *, output)            Pointer to blue intensity (0.0-1.0) of the colour
	  
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