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.