Written by Paul Bourke
September 1992
This document is also
available in Russian,
thanks to Sergey Paramonov.
(You will need the Russian font set!)
HPGL is the HP graphics language designed for specifying 2D graphical information for the HP range of plotters. It was not intended as an interchange format but some software suppliers use it as such. At least it is efficient and easy to write and read. This short note describes those aspects of the format which may be used to describe geometry. The language itself has a large number of instructions, most of the ones not touched on here relate directly to plotter devices, for a full description of the language the HPGL description is normally provided with an HPGL compatable plotter.
HPGL commands are basically two uppercase character instructions followed by any arguments, and finally ending in the separator character which is a semicolon by default. The arguments are normally separated by commas. String arguments are normally terminated by carriage return.
In what follows, all the standard HPGL commands are listed, those which are likely to be useful for data interchange will be discussed at the end of this document. Optional arguments for any command are shown in brackets.
Instruction Arguments
AA Arc Absolute x,y,angle(,tolerance)
AF Advance page
AH Advance page
AP Automatic Pen Operations n
AR Arc Relative x,y,angle(,tolerance)
AS Acceleration Select acceleration(,pennumber)
BF Buffer Plot
BL Buffer label string
CA Select Alternative Charset set
CC Character chord angle angle
CI Circle radius(,tolerance)
CM Character Selection Mode switchmode(,fallbackmode)
CP Character Plot spaces,lines
CS Select Standard Charset set
CT Chord Tolerance n
CV Curved line generator n(,inputdelay)
CD Digitize Clear
DF Default
DI Absolute Direction run,rise
DL Define Download character charnumber(,pencontrol),x,y(...)
DP Digitze Point
DR Relative Direction run.rise
DS Designate Charset slot,set
DT Define Label Terminator terminator
EA Edge Rectangle Absolute x,y
EP Edge Polygon
ER Edge Rectangle Relative x,y
ES Extra Space spaces(,lines)
EW Edge Wedge radius,startangle,sweepangle(,tolerance)
FP Fill Polygon
FS Force Select force(.pennumber)
FT Fill Type type(,spacing(,angle))
GC Group Count countnumber
GM Graphics Memory (polygonbuff)(,downloadbuff)(,replotbuff)(,vectorbuff)
GP Group Pen (groupnumber(,pennumber(,numberofpens,(length))))
IM Input Mask emaskvalue(,smaskvalue(,pmaskvalue))
IN Initialize
IP Input p1 and p2 x,y(,x,y)
IV Invoke Character Slot slot,(left)
IW Input Window x,y,x,y
KY Define Key key(,function)
LB Label string
LO Label Origin positionnumber
LT Line Type patternnumber(,patternlength)
NR Not Ready
PA Plot Absolute x,y(,...)
PB Print Buffered Label
PD Pen Down x,y(,...)
PG Page Feed n
PM Polygon Mode n
PR Plot Relative x,y(,...)
PT Pen Thickness thickness
PU Pen Up x,y(,...)
RA Fill Rectangle Absolute x,y
RO Rotate Coordinate System n
RP Replot n
RR Fill Rectangle Relative x,y
SA Select Alternative Charset
SC Scale x,y,x,y(,type(,left,bottom))
SG Select Pen Group groupnumber
SI Absolute Character Size width,height
SL Character Slant tantheta
SM Symbol Mode character
SP Select Pen pennumber
SR Relative Character Size width,height
SS Select Standard Charset
TL Tick Length tp(,tn)
UC User Defined Character (pencontrol,)x,y
UF User Defined Fill gap1(,gap2,...gap20)
VS Velocity Select speed(,pennumber)
WD Write to Display string
WG Fill Wedge radius,startangle,sweepangle(,tolerance)
XT X Tick
YT Y Tick
The following instructions don't have any arguments but rather generate output from the plotting device. They are of no use for interchanging geometric data and therefore the form of the output is not discussed. See an HPGL reference book.
OA Output Actual Position OC Output Position OD Output Digitised Point OE Output Error OF Output Factors OG Output Group Count OH Output HardClip Limits OI Output Identification OK Output Key OL Output Label Length OO Output Options OP Output p1 and p2 OS Output Status OT Output Carousel Type OW Output Window
The following escape sequences are generally only applicable when connected through a serial interface to a physical plotter, they have nothing to do with data interchange and so their arguments will not be listed nor will the form of the output most of them create .
esc@ Set Plotter Configuration escA Output Identification escB Output Buffer Space escE Output Extended error escH Set Handshake Mode 1 escI Set Handshake Mode 2 escJ Abort Device Control escK Abort Graphics escL Output Buffer Size When Empty escM Set Output Mode escN Set Extended Output and Handshake Mode escO Output Extended Status escP Set Handshake Mode escQ Set Monitor Mode escR Reset escS Output Configurable Memory escT Allocate Configurable Memory escU End Flush Mode escY Plotter On esc( Plotter On escZ Plotter Off esc) Plotter Off
Since plotters are very basic line drawing hardware devices it is not surprising that the most commonly used commands are those that draw lines from one point to another.
This operation is controlled by 4 commands,
Pen up and down dictate when a line is actually being created, the plot commands do the movement between points.
For example to draw a line from (1,0) to (2,0) might be specified as follows
There are two basic attributes that can be assigned to a line, as expected they are actually applied to the pens of the plotting device. They are:
SP - pen number
The pen number normally acts as an indexed colour system, most commonly there are only 8 pens (colour) available.
The other geometry that can be specified is
There are a large number of settings for controlling text, these and further details of the above instructions will be left to the reader to experiment with or read in the full HPGL manuals.