aUCBLogo Demos and Tests / hsbtest

to hsbtest
   cs ht setsc 0
   disls
   setpensize [1 1]
   brightness=1
   repeat 100
   [   sat=repcount/100
      pu lt 90 fd 360 rt 180 pd
      repeat 360
      [   hue=repcount*1-1
         ;c=hsb2 hue sat brightness
         ;setpc rgb c.1 c.2 c.3
         setpc hsb hue sat brightness
         fd 2
      ]
      pu lt 180 fd 360 rt 90 pd
      pu fd 1 pd
   ]
end

to hsb2 :h :s :b_
   local [h2 L x y z r g b]
   h=(mod :h 360)/120
   h2=mod :h 1
   ifelse h2 < 0.5
   [   L=b_*(1+s*h2)
      s=s/(1+s*h2)   ;s>0, h2>0 always so never s/0
      x=1+(-1-h2)*s   y=1-h2*s   z=1-(1-h2)*s
   ][   L=b_*(1+s*(1-h2))
      s=s/(1+s*(1-h2))
      y=1-h2*s   z=1-(1-h2)*s   x=1-(2-h2)*s
   ]
   x=x*L    y=y*L   z=z*L
   ifelse :h < 1
   [   b=x r=y g=z
   ][   ifelse :h < 2
      [   r=x   g=y   b=z
      ][   g=x   b=y   r=z
      ]
   ]
   if r < 0 [r=0]
   if g < 0 [g=0]
   if b < 0 [b=0]
   if r > 1 [r=1]
   if g > 1 [g=1]
   if b > 1 [b=1]
   output (list r g b)
end