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The behavior of graph
is affected by several environment
variables. We have already mentioned the environment variables
BITMAPSIZE
, PAGESIZE
, BG_COLOR
,
EMULATE_COLOR
, MAX_LINE_LENGTH
, and ROTATION
.
They serve as backups for the several options ‘--bitmap-size’,
‘--page-size’, ‘--bg-color’, ‘--emulate-color’,
‘--max-line-length’, and ‘--rotation’. The remaining
environment variables are specific to individual output formats.
graph -T X
, which pops up a window on an X Window System
display and draws graphics in it, checks the DISPLAY
environment variable. The value of this variable determines the display
on which the window will be popped up.
graph -T png
and graph -T gif
, which produce output in PNG
and pseudo-GIF format respectively, are affected by two environment
variables. If the value of the INTERLACE
variable is "yes", the
output file will be interlaced. Also, if the value of the
TRANSPARENT_COLOR
environment variable is the name of a color
that appears in the output file, that color will be treated as
transparent by most applications. For information on what color names
are recognized, see Color Names.
graph -T pnm
, which produces output in Portable Anymap
(PBM/PGM/PPM) format, is affected by the PNM_PORTABLE
environment
variable. If its value is "yes", the output file will be in the
portable (human readable) version of PBM, PGM, or PPM format, rather
than the default (binary) version.
graph -T cgm
, which produces CGM files that comply with the
WebCGM profile for Web-based vector graphics, is affected by two
environment variables. By default, a version 3 CGM file is
generated. Many older CGM interpreters and viewers, such as the ones
built into Microsoft Office and other commercial software, only support
version 1 CGM files. The CGM_MAX_VERSION
environment
variable may be set to "1", "2", "3", or "4" (the default) to
specify an maximum value for the version number. The
CGM_ENCODING
variable may also be set, to specify the type of
encoding used in the CGM file. Supported values are "clear_text" (i.e.,
human readable) and "binary" (the default). The WebCGM profile requires
that the binary encoding be used.
graph -T pcl
, which produces PCL 5 output for
Hewlett–Packard printers, is affected by the environment variable
PCL_ASSIGN_COLORS
. It should be set to "yes" when producing
PCL 5 output for a color printer or other color device. This will
ensure accurate color reproduction by giving the output device complete
freedom in assigning colors, internally, to its “logical pens”. If it
is "no" then the device will use a fixed set of colored pens, and will
emulate other colors by shading. The default is "no" because monochrome
PCL 5 devices, which are more common than colored ones, must use
shading to emulate color.
graph -T hpgl
, which produces Hewlett–Packard Graphics Language
output, is also affected by several environment variables. The most
important is HPGL_VERSION
, which may be set to "1", "1.5", or "2" (the default). "1" means that the output should be generic
HP-GL, "1.5" means that the output should be suitable for the
HP7550A graphics plotter and the HP758x, HP7595A and HP7596A drafting
plotters (HP-GL with some HP-GL/2 extensions), and "2" means that
the output should be modern HP-GL/2. If the version is "1" or "1.5" then the only available fonts will be vector fonts, and all lines
will be drawn with a default thickness (the ‘-W’ option will not
work). Additionally, if the version is "1" then the filling of
arbitrary curves with solid color will not be supported (the ‘-q’
option may be used to fill circles and rectangles aligned with the
coordinate axes, though).
The position of the graph -T hpgl
graphics display on the page
can be rotated 90 degrees counterclockwise by setting the
HPGL_ROTATE
environment variable to "yes". This is not the same
as the rotation obtained with the ‘--rotation’ option, since it
both rotates the graphics display and repositions its lower left corner
toward another corner of the page. Besides "no" and "yes", recognized
values for the HPGL_ROTATE
variable are "0", "90", "180", and "270". "no" and "yes" are equivalent to "0" and "90",
respectively. "180" and "270" are supported only if HPGL_VERSION
is "2" (the default).
Opaque filling and the drawing of visible white lines are
supported only if HPGL_VERSION
is "2" (the default) and the
environment variable HPGL_OPAQUE_MODE
is "yes" (the default).
If the value is "no" then opaque filling will not be used, and white
lines (if any), which are normally drawn with pen #0, will not
be drawn. This feature is to accommodate older HP-GL/2 devices.
HP-GL/2 pen plotters, for example, do not support opacity or the use
of pen #0 to draw visible white lines. Some older HP-GL/2 devices
reportedly malfunction if asked to draw opaque objects.
By default, graph -T hpgl
will draw with a fixed set of pens.
Which pens are present may be specified by setting the HPGL_PENS
environment variable. If HPGL_VERSION
is "1", the default
value of HPGL_PENS
is "1=black"; if HPGL_VERSION
is
"1.5" or "2", the default value of HPGL_PENS
is
"1=black:2=red:3=green:4=yellow:5=blue:6=magenta:7=cyan". The format
should be self-explanatory. By setting HPGL_PENS
, you may
specify a color for any pen in the range #1...#31. For information
on what color names are recognized, see Color Names. Pen #1
must always be present, though it need not be black. Any pen in
the range #2...#31 may be omitted.
If HPGL_VERSION
is "2" then graph -T hpgl
will also be
affected by the environment variable HPGL_ASSIGN_COLORS
. If the value of this variable is "yes", then graph -T hpgl
will not
be restricted to the palette specified in HPGL_PENS
: it will
assign colors to “logical pens” in the range #1...#31, as needed. The default value is "no" because other than color LaserJet
printers and DesignJet plotters, not many HP-GL/2 devices allow the
assignment of colors to logical pens. In particular, HP-GL/2 pen
plotters do not.
graph -T tek
, which produces output for a Tektronix terminal or
emulator, checks the TERM
environment variable. If the value
of TERM
is a string beginning with "xterm", "nxterm", or "kterm",
it is taken as a sign that graph
is running in an X Window System VT100 terminal emulator: an xterm
,
nxterm
, or kterm
. Before drawing graphics, graph -T
tek
will emit an escape sequence that causes the terminal emulator's
auxiliary Tektronix window, which is normally hidden, to pop up.
After the graphics are drawn, an escape sequence that returns control to
the original VT100 window will be emitted. The Tektronix window will
remain on the screen.
If the value of TERM
is a string beginning with "kermit",
"ansi.sys", or "nansi.sys", it is taken as a sign that graph
is running in the VT100 terminal emulator provided by the MS-DOS version
of kermit
. Before drawing graphics, graph -T tek
will
emit an escape sequence that switches the terminal emulator to Tektronix
mode. Also, some of the Tektronix control codes emitted by graph
-T tek
will be kermit
-specific. There will be a limited amount
of color support, which is not normally the case (the 16 ansi.sys
colors will be supported). After drawing graphics, graph -T tek
will emit an escape sequence that returns the emulator to VT100 mode.
The key sequence `ALT minus' can be employed manually within
kermit
to switch between the two modes.