File:Seven-sixfold-spirals-stroked.svg

Converted from the following self-authored PostScript vector source code:

%!
/archimdouble{
%%%%%%%%%%%%%%%%
% PostScript program to display an Archimedean spiral by approximating
% it with Bezier curves.  Can display a double spiral (two spirals
% rotated by 180 degrees with respect to each other).
%%%  Parameters:
                 % centerx = horizontal coordinate of center of spiral
                 % centery = vertical coordinate of center of spiral
                 % rotf = degrees to rotate
/sepwid 110 def  % width separating successive turnings of spiral
                 % (half this if double spiral is selected)
/incrm 30 def    % insert a curve point after this number of degrees
% /sweeps        % number of 360 degree turnings to show
/double 1 def    % change to 0 to display single spiral
/triple 1 def    % change to 0 to for non-triple inner spiral
%%%  Procedures:
/pi 3.1415926535898 def/radians 57.295779513082 def
/sepwid sepwid pi div 2 div def
gsave centerx centery translate rotf rotate
/aspiral{/first 1 def
    lower incrm sweeps 360 mul{8{dup}repeat
        phase add cos/costh exch def
        phase add sin/sinth exch def
        costh mul radians div/thcosth exch def
        sinth mul radians div/thsinth exch def
        thcosth sepwid mul/x exch def
        thsinth sepwid mul/y exch def
        0 eq phase 90 eq phase 270 eq or and{/slope 999999999 def}{/slope
        sinth thcosth add costh thsinth sub div def}ifelse
        sinth 0 gt sinth 0 eq costh -1 eq and or{/flag -1 def}{/flag 1
            def}ifelse
        /A exch def phase 0 eq phase 180 eq or {A 49.29348 lt A 180 gt A
            196.273450852 lt and A 360 gt A 368.8301 lt and A 540 gt A
            545.9907 lt and A 720 gt A 724.5217 lt and A 900 gt A
            903.6281968 lt and or or or or or{/flag flag neg def}if}if
            phase 120 eq phase 300 eq or{A 10 lt A 80 gt A 100 lt and
            or{/flag flag neg def}if}if
        incrm sub 3{dup}repeat phase add cos sepwid mul mul radians div
            /prevx exch def phase add sin sepwid mul mul radians div
            /prevy exch def
        incrm add 3{dup}repeat phase add cos sepwid mul mul radians div
            /nextx exch def phase add sin sepwid mul mul radians div
            /nexty exch def
        /prevdist x prevx sub dup mul y prevy sub dup mul add sqrt pi
            div def
        /nextdist x nextx sub dup mul y nexty sub dup mul add sqrt pi
            div def
        /normaliz slope slope mul 1 add sqrt def
        0 eq{0 0 moveto/prevbezx phase cos nextdist mul def/prevbezy
            phase sin nextdist mul def/first 0 def}{first 1 eq{x y
            moveto/first 0 def}{prevbezx prevbezy x 1 flag mul
            normaliz div prevdist mul sub y slope flag mul normaliz
            div prevdist mul sub x y curveto}ifelse
        /prevbezx x 1 flag mul normaliz div nextdist mul add def
        /prevbezy y slope flag mul normaliz div nextdist mul add def}ifelse}
    for stroke}def
%%% If different sweeps parameter for other spirals, define here:
X grestore
%%%%%%%%%%%%%%%%
}def
.8 dup scale
%-4.12 rotate
%-382.5 -495 translate
9.16666667 setlinewidth
/X{
/sweeps 1.26 def/phase 0 def aspiral
double 0 ne{/sweeps 1.09 def/phase 180 def aspiral}if
triple 0 ne{/sweeps 1.26 def/phase 120 def aspiral
double 0 ne{/sweeps 1.09 def/phase 300 def aspiral}if
            /sweeps 1.26 def/phase 240 def aspiral
double 0 ne{/sweeps 1.09 def/phase 60 def aspiral}if} if}def
/lower 0 def
/centerx 382.5 def/centery 495 def/rotf 0 def
archimdouble
/centerx 382.5 def/centery 495 def/rotf 60 def
archimdouble
/X{
/sweeps 1.1 def/phase 0 def aspiral
double 0 ne{/sweeps 1.29 def/phase 180 def aspiral}if
triple 0 ne{/sweeps 1.45 def/phase 120 def aspiral
double 0 ne{/sweeps 1.09 def/phase 300 def aspiral}if
            /sweeps 1.26 def/phase 240 def aspiral
double 0 ne{/sweeps .95 def/phase 60 def aspiral}if} if}def
/centerx 382.5 def/centery 751.667 def/rotf 300 def
archimdouble
/centerx 160.219858 def/centery 366.666 def/rotf 60 def
archimdouble
/centerx 604.780142 def/centery 366.666 def/rotf 180 def
archimdouble
/X{
/sweeps 1.26 def/phase 0 def aspiral
double 0 ne{/sweeps .95 def/phase 180 def aspiral}if
triple 0 ne{/sweeps 1.1 def/phase 120 def aspiral
double 0 ne{/sweeps 1.29 def/phase 300 def aspiral}if
            /sweeps 1.45 def/phase 240 def aspiral
double 0 ne{/sweeps 1.09 def/phase 60 def aspiral}if} if}def

/centerx 382.5 def/centery 238.333 def/rotf 0 def
archimdouble
/centerx 160.219858 def/centery 623.334 def/rotf 240 def
archimdouble
/centerx 604.780142 def/centery 623.334 def/rotf 120 def
archimdouble
showpage
%EOF