
plrgbhls: Convert RGB color to HLS 

DESCRIPTION:

    This function is used in example 2. 

SYNOPSIS:

plrgbhls(r, g, b, p_h, p_l, p_s)

ARGUMENTS:

    r (PLFLT, input) :      Red intensity (0.0-1.0) of the colour 

    g (PLFLT, input) :      Green intensity (0.0-1.0) of the colour 

    b (PLFLT, input) :      Blue intensity (0.0-1.0) of the colour 

    p_h (PLFLT *, output) :    Pointer to hue, in degrees on the colour
    cone (0.0-360.0) 

    p_l (PLFLT *, output) :    Pointer to lightness, expressed as a
    fraction of the axis of the colour cone (0.0-1.0) 

    p_s (PLFLT *, output) :    Pointer to saturation, expressed as a
    fraction of the radius of the colour cone (0.0-1.0) 
