PIC(1) General Commands Manual PIC(1)
NAME
pic - compile pictures for troff or TeX
SYNOPSIS
pic [ -nvCSU ] [ filename ... ]
pic -t [ -cvzCSU ] [ filename ... ]
DESCRIPTION
This manual page describes the GNU version of pic, which is part of the groff document formatting system. pic
compiles descriptions of pictures 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 user's responsibility to provide appropriate definitions of the PS and PE macros. When the macro
package being used does not supply such definitions (for example, old versions of -ms), appropriate defini‐
tions can be obtained with -mpic: These will center each picture.
OPTIONS
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 Don't use the groff extensions to the troff drawing commands. You should use this if you are using a
postprocessor that doesn't 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 transpar‐
ently. 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 thick‐
ness (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-nega‐
tive 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 this.
-T dev Generate output for the troff device dev. This is unnecessary because the troff output generated by
pic is device-independent.
USAGE
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 file
\centerline{\raise 1em\box\graph}
would avoid this.
To make the vbox having a positive height and a depth of zero (as used e.g. by LaTeX's graphics.sty), define
the following macro in your document:
\def\gpicbox#1{%
\vbox{\unvbox\csname #1\endcsname\kern 0pt}}
Now you can simply say \gpicbox{graph} instead of \box\graph.
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 treatment.
Commands
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 incre‐
ment 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. The value of expr3 can be negative for the additive
case; variable is then tested whether it is greater than or equal to expr2. For the multiplicative
case, expr3 must be greater than zero. If the constraints aren't met, the loop isn't executed. 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 expres‐
sion, 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. For example,
.PS
x = 14
command ".ds string x is " x "."
.PE
\*[string]
prints
x is 14.
sh X command X
Pass command to a shell. X can be any character not occurring in command.
.PS
copy thru % circle at ($1,$2) % until "END"
1 2
3 4
5 6
END
box
.PE
is equivalent to
.PS
circle at (1,2)
circle at (3,4)
circle at (5,6)
box
.PE
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
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 control 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 argu‐
ment 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 variable 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:
.PS
x = 3
y = 3
[
x := 5
y = 5
]
print x " " y
.PE
prints
5 3
The syntax for expressions has been significantly extended:
x ^ y (exponentiation)
sin(x)
cos(x)
atan2(y, x)
log(x) (base 10)
exp(x) (base 10, ie 10^x)
sqrt(x)
int(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)
!e
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 equivalent 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 variables 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 valid.
There is no limit to the depth to which blocks can be examined. For example,
[A: [B: [C: box ]]] with .A.B.C.sw at 1,2
Boxes can have slanted sides. This effectively changes the shape of a box from a rectangle to an arbitrary
parallelogram. The xslanted and yslanted attributes specify the x and y offset of the box's upper right cor‐
ner from its default position.
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) appropriate 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 thick‐
ness 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 supported 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 or slanted sides), 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 proportionally 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 invis‐
ible 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 isn't 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).
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 therefore 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, or gropdf. 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 `expr'th is also allowed. Note that 'th is a single token: no space is allowed
between the ' and the th. For example,
for i = 1 to 4 do {
line from `i'th box.nw to `i+1'th box.se
}
CONVERSION
To obtain a stand-alone picture from a pic file, enclose your pic code with .PS and .PE requests; roff config‐
uration 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 pos‐
sibilities if you first transform 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 con‐
version 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=<devname>
Call
gs --help
for a list of the available devices.
An alternative may be to use the -Tpdf option to convert your picture directly into PDF format. The MediaBox
of the file produced can be controlled by passing a -P-p papersize to groff.
As the Encapsulated PostScript File Format EPS is getting more and more important, and the conversion wasn't
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.
Tpic: Pic for TeX
Brian W. Kernighan, PIC — A Graphics Language for Typesetting (User Manual). AT&T Bell Laboratories, Comput‐
ing Science Technical Report No. 116
<http://cm.bell-labs.com/cm/cs/cstr/116.ps.gz> (revised May, 1991).
ps2eps is available from CTAN mirrors, e.g.
<ftp://ftp.dante.de/tex-archive/support/ps2eps/>
W. Richard Stevens, Turning PIC Into HTML
<http://www.kohala.com/start/troff/pic2html.html>
W. Richard Stevens, Examples of picMacros
<http://www.kohala.com/start/troff/pic.examples.ps>
BUGS
Input characters that are invalid for groff (i.e., 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 edition Unix, which interprets 0 as black
and 1 as white.
PostScript® is a registered trademark of Adobe Systems Incorporation.
Groff Version 1.22.2 7 February 2013 PIC(1)
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