The behavior of
plot is affected by several environment
variables. We have already mentioned the environment variables
MAX_LINE_LENGTH. They serve as backups for the options
`--bitmap-size', `--page-size', `--bg-color', and
`--max-line-length'. The remaining environment variables are
specific to individual output formats.
plot -T X, which pops up a window on an X Window System
display and draws graphics in it, checks the
environment variable. The value of this variable determines the display
on which the window will be popped up.
plot -T pnm, which produces output in Portable Anymap
(PBM/PGM/PPM) format, is affected by the
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.
plot -T gif, which produces output in pseudo-GIF format, is
affected by two environment variables. If the value of the
INTERLACE variable is "yes", the pseudo-GIF output file will be
in interlaced format. 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 that read GIF files. For information
on what color names are recognized, see section Specifying Colors by Name.
plot -T pcl, which produces PCL 5 output for Hewlett--Packard
printers and plotters, is affected by several environment variables.
The position of the graphics display on the page can be adjusted by
variables, which may be specified in centimeters, millimeters, or
inches. For example, an offset could be specified as "2cm" or "1.2in".
Also, the display can be rotated 90 degrees counterclockwise on the
page by setting the
PCL_ROTATE environment variable to "yes".
Besides "no" and "yes", recognized values for this variable are "0",
"90", "180", and "270". "no" and "yes" are equivalent to "0"
and "90", respectively.
PCL_ASSIGN_COLORS is also recognized. 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 much more common than colored ones, must use shading to
plot -T hpgl, which produces Hewlett--Packard Graphics Language
output, is also affected by several environment variables. The most
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 (circles and
rectangles aligned with the coordinate axes may be filled, though).
The position of the
plot -T hpgl graphics display on the page can
be adjusted by setting the
environment variables, which may be specified in centimeters,
millimeters, or inches. For example, an offset could be specified as
"2cm" or "1.2in". Also, the display can be rotated 90 degrees
counterclockwise on the page by setting the
environment variable to "yes". Besides "no" and "yes", recognized
values for this 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
Opaque filling and the drawing of visible white lines are
supported only if
HPGL_VERSION is "2" (the default) and the
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.
plot -T hpgl will draw with a fixed set of pens.
Which pens are present may be specified by setting the
environment variable. If
HPGL_VERSION is "1", the default
HPGL_PENS is "1=black"; if
HPGL_VERSION is "1.5"
or "2", the default value of
"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 section Specifying Colors by Name. Pen #1
must always be present, though it need not be black. Any other pen in
the range #1...#31 may be omitted.
HPGL_VERSION is "2" then
plot -T hpgl will also be
affected by the environment variable
the value of this variable is "yes", then
plot -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.
plot -T tek, which produces output for a Tektronix terminal or
emulator, checks the
TERM environment variable. If the value
TERM is "xterm", "xterms", or "kterm", it is taken as a
sign that the current application is running in an X Window System
VT100 terminal emulator: an
xterm. Before drawing graphics,
plot -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 "kermit", "ansi.sys", "ansissys",
"ansi.sysk", or "ansisysk", it is taken as a sign that the current
application is running in the VT100 terminal emulator provided by the
MS-DOS version of
kermit. Before drawing graphics,
tek will emit an escape sequence that switches the terminal emulator to
Tektronix mode. Also, some of the Tektronix control codes emitted by
plot -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,
plot -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.
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