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 definitions
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 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-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
/usr/share/doc/groff/1.19.2/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. Use the figname command to change
the name of the vbox. You must yourself print that vbox using, for
example, the command
\centerline{\box\graph}
Actually, since the vbox has a height of zero (it is defined with \vtop)
this will produce slightly more vertical space above the picture than
below it;
\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 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. 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 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. 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.
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 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
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 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
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, ellipses, and arcs can be dotted or dashed. In TeX mode splines
can be dotted or dashed also.
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) 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 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 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 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).
To change the name of the vbox in TeX mode, set the pseudo-variable
figname (which is actually a specially parsed command) within a picture.
Example:
.PS
figname = foobar;
...
.PE
The picture is then available in the box \foobar.
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® 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=<devname>
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 graphics
format using the tools of the netpbm package .
FILES
/usr/share/groff/1.19.2/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 <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 1.19.2 19 July 2004 PIC(1)