HPGL vs HPGL/2
HPGL was developed by Hewlett Packard to drive its family of pen plotters. Most commands are vector oriented - pick up the pen, put down the pen, move here, move there. Very few complex commands are part of HPGL since the original plotters did not include powerful CPUs.
HPGL/2 was developed as a successor to HPGL to support many more advanced features that could be offloaded to plotters with powerful CPU's and large amounts of memory. HPGL/2 also includes quite a lot of raster controls and commands since most modern plotters are actually raster devices. This includes embedded pen definitions (up to 256 since a raster device can never run out of pens...) fill patterns, screened vectors, clipping windows, data transformation and the like.
Most plotter drivers do not take advantage of the advanced HPGL/2 functions since they are based on old code that originally supported basic HPGL. However one very popular HPGL/2 command that is often used is PE - poyline encoded command.
PE is very popular because it compresses the pen movement commands by encoding them. This significantly reduces the plot file size. However PE is more difficult to decode which is why many low cost (or no cost) HPGL to DXF programs don't properly support it. Needless to say, HP2DXF does support the PE command.
Supported HPGL/HPGL2 Commands
Command HPGL HPGL2 Description SP x x Selects a pen; data mapped to AutoCAD layer layer no=10 x pen number + | line-type| PA x x move pen absolute PR x x move pen relative to current coordinates PE x polyline encoded - a series of movements encoded to minimize bytes used. PU x x pen up PD x x pen down - any moves with pen down generate arcs, polyines PW x pen width - translated to polyline with width IP x x new user unit scale factor AA x x arc absolute AR x x arc relative EA x x outline of rectangle translated to a zero width closed polyline LB x x string of text - to DXF text DT x x string termination character SI x x character height DI x x direction (angle) of text CS x x text scaling parameter CI x x circle SC x x scale factor LT x x line type - indirectly supported by mapping to a unique AutoCAD layer.
Special Notes and Behavior
Command Line UsageHP2DXf is run from the UNIX command line. Syntax:
hp2dxf [input_file] [output_file] [options] where input_file the hpgl file to translate output_file name of the DXF file. If not present the input file name with suffix .dxf is used. options -s scale factor. Defaults to 1.0 -p create a "closed" polyline if first/last point of a list of draws meet. -d disable automatic arc recognition.
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