%!
%%BoundingBox: 126 246 486 546
% Cookbook Example Program from First Printing, Revised 7 Jan 1985
% Program: Drawing a Pie Chart Number: 18
%-----------------------------------------------------------------------------
%
/PieDict 24 dict def % Local storage for
% ``DrawPieChart'' and its related
% procedures.
PieDict begin
/DrawSlice % DrawSlice draws an outlined and
{ /grayshade exch def % filled-in pie slice. It takes
/endangle exch def % four operands: the label for
/startangle exch def % this particular pie slice, the
/thelabel exch def % starting angle for the slice,
% the ending angle for the slice
% and the shade of gray the slice
% should be.
newpath % Create a path which will draw a
% pie slice.
0 0 moveto
0 0 radius startangle endangle arc
closepath
1.415 setmiterlimit % This guarantees that when we
% outline the pie slices with a
% stroke that we will not get a
% spike on the interior angles.
gsave grayshade setgray fill grestore % Fill the pie slice path with the
stroke % appropriate gray color. By using
% gsave and grestore we don't lose
% the current path. Since
% PostScript paints color onto the
% page, it is very important that
% we fill the pie slice first and
% then outline it with a stroke.
gsave % Draw the tick mark and place the
% label:
startangle endangle add 2 div % Find the center of the pie slice
rotate % and rotate so that the x-axis
% coincides with this center.
radius 0 translate % Translate the origin out to the
% circumference.
newpath
0 0 moveto labelps .8 mul 0 lineto% Draw the tick-mark.
stroke
labelps 0 translate % Move the origin out a little
% beyond the circumference.
0 0 transform % Next we wish to place the label
grestore % at the current origin. If we
itransform % simply draw the text on the page
/y exch def /x exch def % now, it would come out rotated.
x y moveto % Since this is not desired we
% avoid it by returning to the
% previous unrotated coordinate
% system. Before returning,
% though, we would like to
x 0 lt % remember the position of the
{ thelabel stringwidth pop neg % current origin on the printed
0 rmoveto % page. We will accomplish this by
} if % using the transform and
% itransform operators. Performing
% a transform on the origin pushes
% the coordinates of the origin in
% device space onto the operand
% stack. Performing a grestore
% returns us to the previous
% unrotated coordinate system.
% Next we perform an itransform on
% the two device coordinates left
% on the stack to determine where
% we are in the current coordinate
% system.
y 0 lt { 0 labelps neg rmoveto } if % Make some adjustments so that
thelabel show % the label text won't collide
} def % with the pie slice.
/findgray % Procedure findgray calculates
{ /i exch def /n exch def % the gray value for a slice. It
i 2 mod 0 eq % takes two arguments: the total
{ i 2 div n 2 div round add n div } % number of slices and the current
{ i 1 add 2 div n div } % slice number (Given that there
ifelse % are n pie slices, the slices are
} def % ``numbered'' from 1 to n). The
end % gray values for the pie slices
% range evenly from white to black
% (i.e. - the values provided to
% setgray range from (n/n, n-1/n,
% ..., 1/n)). Since we don't want
% similar values of gray next to
% each other, findgray
% ``shuffles'' the possible
% combinations of gray.
/DrawPieChart % DrawPieChart takes seven
{ PieDict begin % arguments: the title of the pie
/radius exch def % chart, the point size to print
/ycenter exch def /xcenter exch def % the title in, the point size to
/PieArray exch def % print the labels for each slice
/labelps exch def /titleps exch def % in, a special array (described
/title exch def % below where DrawPieChart is
% called), the (x,y) center of the
% pie chart and the radius of the
% pie chart.
gsave
xcenter ycenter translate % Translate the coordinate system
% origin to center of pie chart.
/Helvetica findfont titleps % Print the title of the pie chart
scalefont setfont % in Helvetica.
title stringwidth pop 2 div neg % Center the title below the pie
% chart.
radius neg titleps 3 mul sub
moveto title show
/Helvetica findfont labelps % Print the individual pie slice
scalefont setfont % labels in Helvetica
/numslices PieArray length def
/slicecnt 0 def
/curangle 0 def % A ``loop'' variable that keeps
% track of the angle of arc to
% begin each pie slice at.
PieArray % Repeat the following for each
% element in the PieArray.
{ /slicearray exch def
slicearray aload pop % Push the label and percentage
% onto the stack.
/percent exch def
/label exch def
/perangle percent 360 mul def % Convert the percentage into
% degrees of angle.
/slicecnt slicecnt 1 add def
label curangle
curangle perangle add
numslices slicecnt findgray
DrawSlice
/curangle curangle perangle add % Update the current starting
% angle.
def
} forall
grestore
end
} def
() 18 9
[ [(Blueberry) .12 ] % The pie array is an array of
[(Cherry) .30 ] % arrays. Each array in the pie
[(Apple) .26 ] % array contains a string denoting
[(Boston Cream) .16 ] % the label to be printed next to
[(Other) .04 ] % the pie slice followed by a real
[(Vanilla Cream) .12 ] % number indicating the percentage
] 306 396 100 DrawPieChart % of the pie represented by this
% particular slice.
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