Ubuntu Manpage: pic - compile pictures for troff or TeX

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®
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

       /usr/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.