pic(1) General Commands Manual pic(1)
Name
pic - compile pictures for troff or TeX
Synopsis
pic [-CnSU] [file ...]
pic -t [-cCSUz] [file ...]
pic --help
pic -v
pic --version
Description
The GNU implementation of pic is part of the groff(1) document
formatting system. pic is a troff(1) preprocessor that translates
descriptions of diagrammatic pictures embedded in roff(7) or TeX input
files into the language understood by TeX or troff. It copies the
contents of each file to the standard output stream, except that lines
between .PS and any of .PE, .PF, or .PY are interpreted as picture
descriptions in the pic language. End a pic picture with .PE to leave
the drawing position at the bottom of the picture, and with .PF or .PY
to leave it at the top. Normally, pic is not executed directly by the
user, but invoked by specifying the -p option to groff(1). If no file
operands are given on the command line, or if file is "-", the standard
input stream is read.
It is the user's responsibility to provide appropriate definitions of
the PS, PE, and one or both of the PF and PY macros. When a macro
package does not supply these, obtain simple definitions with the groff
option -mpic; these will center each picture.
GNU pic supports PY as a synonym of PF to work around a name space
collision with the mm macro package, which defines PF as a page footer
management macro. Use PF preferentially unless a similar problem faces
your document.
Options
--help displays a usage message, while -v and --version show version
information; all exit afterward.
-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.
-C Recognize .PS, .PE, .PF, and .PY even when followed by a
character other than space or newline.
-n Don't use groff extensions to the troff drawing commands.
Specify this option if a postprocessor you're using doesn't
support these extensions, described in groff_out(5). This
option also causes pic not to use zero-length lines to draw dots
in troff mode.
-S Operate in safer mode; sh commands are ignored. This mode,
enabled by default, can be useful when operating on
untrustworthy input.
-t Produce TeX output.
-U Operate in unsafe mode; sh commands are interpreted.
-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. GNU pic always
does this.
-T dev Generate output for the troff device dev. This is unnecessary
because the troff output generated by GNU pic is device-
independent.
Usage
This section primarily discusses the differences between GNU pic and
the Eighth Edition Research Unix version of AT&T pic (1985). Many of
these differences also apply to later versions of AT&T pic.
TeX mode
TeX-compatible output is produced when the -t option is specified. You
must use a TeX driver that supports tpic version 2 specials. (tpic was
a fork of AT&T pic by Tim Morgan of the University of California at
Irvine that diverged from its source around 1984. It is best known
today for lending its name to a group of \special commands it produced
for TeX.)
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 the value of \baselineskip. Anything
else may well produce undesirable results; use at your own risk. By
default, lines beginning with a dot are not treated specially--but see
the -c option.
In TeX mode, pic will define a vbox called \graph for each picture.
Use GNU pic's figname command to change the name of the vbox. You must
print that vbox yourself using the command
\centerline{\box\graph}
for instance. 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 give the vbox a positive height and a depth of
zero (as used by LaTeX's graphics.sty, for example) define the
following macro in your document.
\def\gpicbox#1{%
\vbox{\unvbox\csname #1\endcsname\kern 0pt}}
You can then simply say \gpicbox{graph} instead of \box\graph.
Commands
Several commands new to GNU pic accept delimiters, shown in their
synopses as braces { }. Nesting of braces is supported. Any other
characters (except a space, tab, or newline) may be used as alternative
delimiters, in which case the members of a given pair must be
identical. Strings are recognized within delimiters of either kind;
they may contain the delimiter character or unbalanced braces.
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 and write arguments to the standard error stream
followed by a newline. Each arg must be an expression, a
position, or text. This is useful for debugging.
command arg ...
Concatenate arguments and pass them as a line to troff or TeX.
Each arg must be an expression, a position, or text. command
allows the values of pic variables to be passed to the
formatter. For example,
.PS
x = 14
command ".ds string x is " x "."
.PE
\*[string]
produces
x is 14.
when formatted with troff.
sh X command X
Pass command to a shell.
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
and
.PS
circle at (1,2)
circle at (3,4)
circle at (5,6)
box
.PE
are equivalent. 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. The argument after thru is
looked up as a macro name first; if not defined, its first
character is interpreted as a delimiter.
reset
reset pvar1[,] pvar2 ...
Reset predefined variables pvar1, pvar2 ... to their default
values; if no arguments are given, reset all predefined
variables to their default values. Variable names may be
separated by commas, spaces, or both. Assigning a value to
scale also causes all predefined 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.
var := expr
This syntax resembles variable assignment with = except that var
must already be defined, and expr will be assigned to var
without creating a variable local to the current block. (By
contrast, = defines var in the current block if it is not
already defined there, and then changes the value in the current
block only.) For example,
.PS
x = 3
y = 3
[
x := 5
y = 5
]
print x y
.PE
writes
5 3
to the standard error stream.
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, i.e. 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.
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
corner 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. GNU pic will
always scale a picture by the same amount vertically as well as
horizontally. This is different from 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. Only the modifiers
"#", "-", "+", and " " [space]), a minimum field width, an optional
precision, and the conversion specifiers %e, %E, %f, %g, %G, and %% are
supported.
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 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 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.
Additional modifiers are available to draw colored objects: outline[d]
sets the color of the outline, shaded the fill color, and colo[u]r[ed]
sets both. All expect a subsequent string argument specifying the
color.
circle shaded "green" outline "black"
Color is not yet supported in TeX mode. Device macro files like
ps.tmac declare color names; you can define additional ones with the
defcolor request (see groff(7)).
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. 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(1) or gropdf(1). 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. This attribute will have no effect on
objects whose start and end points are coincident.
In places where nth is allowed, 'expr'th is also allowed. "'th" is a
single token: no space is allowed between the apostrophe 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(1)) 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.
For bitmapped graphic formats, you should use pstopnm; the resulting
(intermediate) pnm(5) file can be then converted to virtually any
graphics format using the tools of the netpbm package.
Files
/opt/local/share/groff/1.23.0/tmac/pic.tmac
offers simple definitions of the PS, PE, PF, and PY macros.
Bugs
Characters that are invalid as input to GNU troff (see the groff
Texinfo manual or groff_char(7) for a list) are rejected even in TeX
mode.
The interpretation of fillval is incompatible with the pic in Tenth
Edition Research Unix, which interprets 0 as black and 1 as white.
See also
/opt/local/share/doc/groff-1.23.0/pic.ps
"Making Pictures with GNU pic", by Eric S. Raymond. This file,
together with its source, pic.ms, is part of the groff
distribution.
"PIC--A Graphics Language for Typesetting: User Manual", by Brian W.
Kernighan, 1984 (revised 1991), AT&T Bell Laboratories Computing
Science Technical Report No. 116
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 pic Macros <http://www.kohala.com/
start/troff/pic.examples.ps>
troff(1), groff_out(5), tex(1), gs(1), ps2eps(1), pstopnm(1),
ps2epsi(1), pnm(5)
groff 1.23.0 2 July 2023 pic(1)
groff 1.23.0 - Generated Sat Dec 23 08:40:02 CST 2023