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       pic - compile pictures for troff or TeX

       pic [ -nvCSU ] [ filename ... ]
       pic -t [ -cvzCSU ] [ filename ... ]

       This manual page describes the GNU version of pic, which is part of the
       groff document formatting system.  pic compiles	descriptions  of  pic
       tures  embedded	within troff or TeX input files into commands that are
       understood by TeX or troff.  Each picture starts with a line  beginning
       with  .PS and ends with a line beginning with .PE.  Anything outside of
       .PS and .PE is passed through without change.

       It is the users responsibility to provide appropriate  definitions  of
       the  PS and PE macros.  When the macro package being used does not sup
       ply such definitions (for example, old versions	of  -ms),  appropriate
       definitions can be obtained with -mpic: these will center each picture.

       Options that do not take arguments may be grouped behind  a  single  -.
       The  special  option  -- can be used to mark the end of the options.  A
       filename of - refers to the standard input.

       -C     Recognize .PS and .PE even when followed by  a  character  other
	      than space or newline.

       -S     Safer mode; do not execute sh commands.  This can be useful when
	      operating on untrustworthy input.  (enabled by default)

       -U     Unsafe mode; revert the default option -S.

       -n     Dont use the groff extensions to the  troff  drawing  commands.
	      You  should  use	this  if  you  are  using a postprocessor that
	      doesnt support these extensions.	The extensions are  described
	      in groff_out(5).	The -n option also causes pic not to use zero-
	      length lines to draw dots in troff mode.

       -t     TeX mode.

       -c     Be more compatible with tpic.  Implies -t.  Lines beginning with
	      \  are not passed through transparently.	Lines beginning with .
	      are passed through with the initial .  changed  to  \.   A  line
	      beginning  with  .ps  is	given  special	treatment: it takes an
	      optional integer argument specifying  the  line  thickness  (pen
	      size)  in  milliinches; a missing argument restores the previous
	      line thickness; the default line	thickness  is  8  milliinches.
	      The  line thickness thus specified takes effect only when a non-
	      negative line thickness has not been specified  by  use  of  the
	      thickness attribute or by setting the linethick variable.

       -v     Print the version number.

       -z     In TeX mode draw dots using zero-length lines.

       The following options supported by other versions of pic are ignored:

       -D     Draw  all  lines	using the \D escape sequence.  pic always does

       -T dev Generate output for the troff device dev.  This  is  unnecessary
	      because the troff output generated by pic is device-independent.

       This section describes only the differences between  GNU  pic  and  the
       original version of pic.  Many of these differences also apply to newer
       versions of Unix pic.  A complete documentation	is  available  in  the


   TeX mode
       TeX  mode  is enabled by the -t option.	In TeX mode, pic will define a
       vbox called \graph for each picture.  You must yourself print that vbox
       using, for example, the command


       Actually,  since  the  vbox  has  a  height  of	zero this will produce
       slightly more vertical space above the picture than below it;

	      \centerline{\raise 1em\box\graph}

       would avoid this.

       You must use a TeX driver that supports the tpic specials, version 2.

       Lines beginning with \ are passed through transparently; a %  is  added
       to  the	end  of the line to avoid unwanted spaces.  You can safely use
       this feature to change fonts or to change the value  of	\baselineskip.
       Anything  else  may  well  produce undesirable results; use at your own
       risk.  Lines beginning with a period are not given any  special	treat

       for variable = expr1 to expr2 [by [*]expr3] do X body X
	      Set variable to expr1.  While the value of variable is less than
	      or equal to expr2, do body and increment variable by  expr3;  if
	      by  is not given, increment variable by 1.  If expr3 is prefixed
	      by * then variable will instead be multiplied by expr3.	X  can
	      be any character not occurring in body.

       if expr then X if-true X [else Y if-false Y]
	      Evaluate	expr;  if it is non-zero then do if-true, otherwise do
	      if-false.  X can be any character not occurring in  if-true.   Y
	      can be any character not occurring in if-false.

       print arg...
	      Concatenate  the	arguments and print as a line on stderr.  Each
	      arg must be an expression, a position, or text.  This is	useful
	      for debugging.

       command arg...
	      Concatenate  the	arguments  and	pass them through as a line to
	      troff or TeX.  Each arg must be an expression,  a  position,  or
	      text.   This  has a similar effect to a line beginning with . or
	      \, but allows the values of variables to be passed through.

       sh X command X
	      Pass command to a shell.	X can be any character	not  occurring
	      in command.

       copy "filename"
	      Include filename at this point in the file.

       copy ["filename"] thru X body X [until "word"]
       copy ["filename"] thru macro [until "word"]
	      This  construct  does  body  once for each line of filename; the
	      line is split into blank-delimited words, and occurrences of  $i
	      in body, for i between 1 and 9, are replaced by the i-th word of
	      the line.  If filename is not given, lines are  taken  from  the
	      current input up to .PE.	If an until clause is specified, lines
	      will be read only until a line the first word of which is  word;
	      that  line  will	then be discarded.  X can be any character not
	      occurring in body.  For example,

		     copy thru % circle at ($1,$2) % until "END"
		     1 2
		     3 4
		     5 6

	      is equivalent to

		     circle at (1,2)
		     circle at (3,4)
		     circle at (5,6)

	      The commands to be performed for each line  can  also  be  taken
	      from  a macro defined earlier by giving the name of the macro as
	      the argument to thru.

       reset variable1[,] variable2 ...
	      Reset pre-defined variables variable1, variable2	...  to  their
	      default  values.	 If  no  arguments  are  given, reset all pre-
	      defined variables to their default values.  Note that  assigning
	      a value to scale also causes all pre-defined variables that con
	      trol dimensions to be reset to their default  values  times  the
	      new value of scale.

       plot expr ["text"]
	      This  is	a  text object which is constructed by using text as a
	      format string for sprintf with an argument of expr.  If text  is
	      omitted  a  format  string  of  "%g" is used.  Attributes can be
	      specified in the same way as for a normal text object.  Be  very
	      careful  that you specify an appropriate format string; pic does
	      only very limited checking of the string.  This is deprecated in
	      favour of sprintf.

       variable := expr
	      This  is	similar  to = except variable must already be defined,
	      and expr will be assigned to variable without creating  a  vari
	      able  local  to  the current block.  (By contrast, = defines the
	      variable in the current block  if  it  is  not  already  defined
	      there,  and  then  changes the value in the current block only.)
	      For example, the following:

		     x = 3
		     y = 3
		       x := 5
		       y = 5
		     print x " " y

	      prints 5 3.

       Arguments of the form

	      X anything X

       are also allowed to be of the form

	      { anything }

       In this case anything can contain balanced  occurrences	of  {  and  }.
       Strings may contain X or imbalanced occurrences of { and }.

       The syntax for expressions has been significantly extended:

       x ^ y (exponentiation)
       atan2(y, x)
       log(x) (base 10)
       exp(x) (base 10, ie 10^x)
       rand() (return a random number between 0 and 1)
       rand(x) (return a random number between 1 and x; deprecated)
       srand(x) (set the random number seed)
       max(e1, e2)
       min(e1, e2)
       e1 && e2
       e1 || e2
       e1 == e2
       e1 != e2
       e1 >= e2
       e1 > e2
       e1 <= e2
       e1 < e2
       "str1" == "str2"
       "str1" != "str2"

       String comparison expressions must be parenthesised in some contexts to
       avoid ambiguity.

   Other Changes
       A bare expression, expr, is acceptable as an attribute; it  is  equiva
       lent to dir expr, where dir is the current direction.  For example

	      line 2i

       means  draw a line 2 inches long in the current direction.  The i (or
       I) character is ignored; to use another	measurement  unit,  set  the
       scale variable to an appropriate value.

       The  maximum  width  and height of the picture are taken from the vari
       ables maxpswid and maxpsht.  Initially these have values 8.5 and 11.

       Scientific notation is allowed for numbers.  For example
	      x = 5e-2

       Text attributes can be compounded.  For example,
	      "foo" above ljust
       is legal.

       There is no limit to the depth to which blocks can  be  examined.   For
	      [A: [B: [C: box ]]] with .A.B.C.sw at 1,2
	      circle at last [].A.B.C
       is acceptable.

       Arcs  now have compass points determined by the circle of which the arc
       is a part.

       Circles and arcs can be dotted or dashed.  In TeX mode splines  can  be
       dotted or dashed.

       Boxes can have rounded corners.	The rad attribute specifies the radius
       of the quarter-circles at each corner.  If no rad or diam attribute  is
       given, a radius of boxrad is used.  Initially, boxrad has a value of 0.
       A box with rounded corners can be dotted or dashed.

       The .PS line can have a second argument specifying a maximum height for
       the  picture.   If  the	width  of  zero is specified the width will be
       ignored in computing the scaling factor for the picture.  Note that GNU
       pic  will  always scale a picture by the same amount vertically as well
       as horizontally.  This is different from the  DWB  2.0  pic  which  may
       scale a picture by a different amount vertically than horizontally if a
       height is specified.

       Each text object has an invisible box associated with it.  The  compass
       points  of  a  text  object  are  determined by this box.  The implicit
       motion associated with the object is also determined by this box.   The
       dimensions  of this box are taken from the width and height attributes;
       if the width attribute is not supplied then the width will be taken  to
       be  textwid;  if  the  height attribute is not supplied then the height
       will be taken to be the number of  text	strings  associated  with  the
       object times textht.  Initially textwid and textht have a value of 0.

       In  (almost  all)  places  where  a  quoted text string can be used, an
       expression of the form

	      sprintf("format", arg,...)

       can also be used; this will produce the arguments  formatted  according
       to format, which should be a string as described in printf(3) appropri
       ate for the number of arguments supplied.

       The thickness of the lines used to draw objects is  controlled  by  the
       linethick  variable.   This  gives the thickness of lines in points.  A
       negative value means use the default thickness:	in  TeX  output  mode,
       this  means  use  a thickness of 8 milliinches; in TeX output mode with
       the -c option, this means use  the  line  thickness  specified  by  .ps
       lines; in troff output mode, this means use a thickness proportional to
       the pointsize.  A zero value means draw the thinnest possible line sup
       ported by the output device.  Initially it has a value of -1.  There is
       also a thick[ness] attribute.  For example,

	      circle thickness 1.5

       would draw a circle using a line with a thickness of 1.5  points.   The
       thickness  of lines is not affected by the value of the scale variable,
       nor by the width or height given in the .PS line.

       Boxes (including boxes with rounded corners), circles and ellipses  can
       be  filled  by  giving  them  an  attribute of fill[ed].  This takes an
       optional argument of an expression with a value between 0 and 1; 0 will
       fill  it with white, 1 with black, values in between with a proportion
       ally gray shade.  A value greater than 1 can also be used:  this  means
       fill  with  the shade of gray that is currently being used for text and
       lines.  Normally this will be black, but output devices may  provide  a
       mechanism  for  changing  this.	Without an argument, then the value of
       the variable fillval will be used.  Initially this has a value of  0.5.
       The  invisible  attribute  does not affect the filling of objects.  Any
       text associated with a filled object will be added after the object has
       been filled, so that the text will not be obscured by the filling.

       Three  additional  modifiers  are available to specify colored objects:
       outline[d] sets the color of the outline, shaded the  fill  color,  and
       colo[u]r[ed]  sets both.  All three keywords expect a suffix specifying
       the color, for example

	      circle shaded "green" outline "black"

       Currently, color support isnt available in TeX mode.  Predefined color
       names  for  groff  are  in the device macro files, for example ps.tmac;
       additional colors can be defined with the .defcolor  request  (see  the
       manual page of troff(1) for more details).

       pic  assumes  that  at  the  beginning of a picture both glyph and fill
       color are set to the default value.

       Arrow heads will be drawn as solid triangles if the variable  arrowhead
       is  non-zero  and  either  TeX mode is enabled or the -n option has not
       been given.  Initially arrowhead has a value  of 1.   Note  that  solid
       arrow heads are always filled with the current outline color.

       The troff output of pic is device-independent.  The -T option is there
       fore redundant.	All numbers are taken to be  in  inches;  numbers  are
       never interpreted to be in troff machine units.

       Objects	can  have  an  aligned	attribute.  This will only work if the
       postprocessor is grops.	Any text associated with an object having  the
       aligned	attribute  will  be  rotated about the center of the object so
       that it is aligned in the direction from the start  point  to  the  end
       point  of the object.  Note that this attribute will have no effect for
       objects whose start and end points are coincident.

       In places where nth is allowed exprth is also allowed.  Note that th
       is  a  single token: no space is allowed between the  and the th.  For

	      for i = 1 to 4 do {
		 line from ith box.nw to i+1th box.se

       To obtain a stand-alone picture from a pic file, enclose your pic  code
       with  .PS and .PE requests; roff configuration commands may be added at
       the beginning of the file, but no roff text.

       It is necessary to feed this file into groff without  adding  any  page
       information,  so you must check which .PS and .PE requests are actually
       called.	For example, the mm macro package adds a page number, which is
       very annoying.  At the moment, calling standard groff without any macro
       package works.  Alternatively, you can define your own  requests,  e.g.
       to do nothing:

	      .de PS
	      .de PE

       groff  itself  does  not  provide direct conversion into other graphics
       file formats.  But there are lots of possibilities if you first	trans
       form  your picture into PostScript format using the groff option -Tps.
       Since this ps-file lacks BoundingBox information it is not very	useful
       by  itself,  but  it may be fed into other conversion programs, usually
       named ps2other or pstoother or  the  like.   Moreover,  the  PostScript
       interpreter  ghostscript  (gs) has built-in graphics conversion devices
       that are called with the option

	      gs -sDEVICE=

	      gs --help

       for a list of the available devices.

       As the Encapsulated PostScript File Format EPS is getting more and more
       important,  and	the conversion wasnt regarded trivial in the past you
       might be interested to know that  there	is  a  conversion  tool  named
       ps2eps  which  does  the  right	job.   It is much better than the tool
       ps2epsi packaged with gs.

       For bitmapped graphic formats, you should use  pstopnm;	the  resulting
       (intermediate) PNM file can be then converted to virtually any graphics
       format using the tools of the netpbm package .

	      Example definitions of the PS and PE macros.

       troff(1),   groff_out(5),   tex(1),   gs(1),   ps2eps(1),   pstopnm(1),
       ps2epsi(1), pnm(5)

       Tpic: Pic for TeX

       Brian  W.  Kernighan,  PIC   A Graphics Language for Typesetting (User
       Manual).  AT&T Bell Laboratories, Computing  Science  Technical	Report
       No. 116		(revised  May,

       ps2eps is available from CTAN mirrors, e.g.

       W. Richard Stevens - Turning PIC Into HTML

       W. Richard Stevens - Examples of picMacros

       Input characters that are invalid for groff (ie those with  ASCII  code
       0, or 013 octal, or between 015 and 037 octal, or between 0200 and 0237
       octal) are rejected even in TeX mode.

       The interpretation of fillval is incompatible with the pic in 10th edi
       tion Unix, which interprets 0 as black and 1 as white.

       PostScript is a registered trademark of Adobe Systems Incorporation.

Groff Version 1.18.1	       20 September 2002			PIC(1)

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