spirals.ps

/radius 0 def
/currentgray 1 def
/pagewidth currentpagedevice /PageSize get 0 get def
/pageheight currentpagedevice /PageSize get 1 get def
 
/incRadius {
    /radius radius 6 add def
} def

/setGray {
    /currentgray radius pagewidth div def
} def


/doCircle {
  0.6 currentgray mul setgray
  
  currentgray 8000 mul rotate
  0 0 -8 radius add 0 30 currentgray mul currentgray 140 mul add arc
  currentgray -8000 mul rotate
  stroke
  
  currentgray 11000 mul rotate
  0 0 -3 radius add 120 currentgray mul 22 currentgray mul currentgray 97 mul add arc
  currentgray -11000 mul rotate
  stroke
  
  currentgray 2200 mul rotate
  0 0 -3 radius add 0 160 currentgray mul 360 arc
  currentgray -2200 mul rotate
  stroke
  
  0.3 0.3 currentgray mul add setgray
  
  currentgray 7000 mul rotate
  0 0 radius 50 360 currentgray 360 mul sub arc
  currentgray -7000 mul rotate
  stroke
  
} def

pagewidth 2 div
pageheight 2 div
translate
0.3 setlinewidth

{
    radius pagewidth le
    {
        doCircle
        incRadius
        setGray
    }
    {
        exit
    } ifelse
} loop


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