gps(4) CLIX gps(4)
NAME
gps - Graphical primitive strings/file format
DESCRIPTION
GPS is a format used to store graphical data. Several routines have been
developed to edit and display GPS files on various devices. Also, higher
level graphics programs such as plot (in stat(1)) and vtoc (in toc(1))
produce GPS format output files.
A GPS is composed of five types of graphical data or primitives.
GPS Primitives
lines The lines primitive has a variable number of points from which
zero or more connected line segments are produced. The first
point given produces a move to that location. (A move is a
relocation of the graphic cursor without drawing.) Successive
points produce line segments from the previous point.
Parameters are available to set color, weight, and style (see
below).
arc The arc primitive has a variable number of points to which a
curve is fit. The first point produces a move to that point.
If only two points are included, a line connecting the points
will result; if three points a circular arc through the points
is drawn; and if more than three, lines connect the points.
(In the future, a spline will be fit to the points if they
number greater than three.) Parameters are available to set
color, weight, and style.
text The text primitive draws characters. It requires a single
point which locates the center of the first character to be
drawn. Parameters are color, font, textsize, and textangle.
hardware The hardware primitive draws hardware characters or gives
control commands to a hardware device. A single point locates
the beginning location of the hardware string.
comment A comment is an integer string that is included in a GPS file
but causes nothing to be displayed. All GPS files begin with a
comment of zero length.
GPS Parameters
color An integer value set for arc, lines, and text primitives.
weight Weight is an integer value set for arc and lines primitives to
indicate line thickness. The value 0 is narrow weight, 1 is
bold, and 2 is medium weight.
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gps(4) CLIX gps(4)
style Style is an integer value set for lines and arc primitives to
give one of the five different line styles that can be drawn
on TEKTRONIX 4010 series storage tubes. They are:
0 solid
1 dotted
2 dot dashed
3 dashed
4 long dashed
font An integer value set for text primitives to designate the text
font to be used in drawing a character string. (Currently
font is expressed as a four-bit weight value followed by a
four-bit style value.)
textsize An integer value used in text primitives to express the size
of the characters to be drawn. The value of textsize
represents the height of characters in absolute universe-units
and is stored at one-fifth this value in the size-orientation
(so) word (see below).
textangle A signed integer value used in text primitives to express
rotation of the character string around the beginning point.
The value of textangle is expressed in degrees from the
positive x-axis and can be a positive or negative value. It
is stored in the size-orientation (so) word as a value 256/360
of it's absolute value.
ORGANIZATION
GPS primitives are organized internally as follows:
lines cw points sw
arc cw points sw
text cw point sw so [string]
hardware cw point [string]
comment cw [string]
cw The Cw control word begins all primitives. It consists of four
bits that contain a primitive-type code and twelve bits that
contain the word-count for that primitive.
point(s) One or more pairs of integer coordinates. The text and
hardware primitives only require a single point. The point(s)
are values within a Cartesian plane or universe having 64K (-
32K to +32K) points on each axis.
2 Intergraph Corporation - 2/94
gps(4) CLIX gps(4)
sw The style-word used in lines, arc, and text primitives. For
all three, eight bits contain color information. In arc and
lines eight bits are divided as four bits weight and four bits
style. In the text primitive eight bits of sw contain the
font.
so The size-orientation word used in text primitives. Eight bits
contain text size and eight bits contain text rotation.
string A null-terminated character string. If the string does not end
on a word boundary, an additional null is added to the GPS file
to insure word-boundary alignment.
RELATED INFORMATION
Commands: graphics(1), stat1), toc(1)
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