Learn the UNIX/Linux command line
Home Man Pages
PIC(1) 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 sup-
ply such definitions (for example, old versions of -ms), appropriate
definitions can be obtained with -mpic: these will center each pic-
ture.
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 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
this.
-T dev Generate output for the troff device dev. This is unnecessary
because the troff output generated by pic is device-indepen-
dent.
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
/usr/share/doc/groff/1.18.1.1/pic.ms
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
\centerline{\box\graph}
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-
ment.
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 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,
.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 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:
.PS
x = 3
y = 3
[
x := 5
y = 5
]
print x " " y
.PE
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 }.
Expressions
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 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
example,
[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) appro-
priate 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
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), 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 pro-
portionally 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 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).
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
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. 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 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
transform your picture into PostScript(R) 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 conver-
sion devices that are called with the option
gs -sDEVICE=
Call
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 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.
For bitmapped graphic formats, you should use pstopnm; the resulting
(intermediate) PNM file can be then converted to virtually any graph-
ics format using the tools of the netpbm package .
FILES
/usr/share/groff/1.18.1.1/tmac/pic.tmac
Example definitions of the PS and PE macros.
SEE ALSO
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,
1991).
ps2eps is available from CTAN mirrors, e.g.
W. Richard Stevens - Examples of picMacros
BUGS
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
edition Unix, which interprets 0 as black and 1 as white.
PostScript(R) is a registered trademark of Adobe Systems Incorporation.
Groff Version 1.18.1.1 20 September 2002 PIC(1)
UNIX/Linux commands referenced on this page: