HP-GL/2 Plot File Format

Written by Allan, Jan 2001

The HP-GL/2 format is the format, which can be read by plotters. The HP-GL/2 format is created when CAD data is saved for printing into a file.

What are HP-GL/2, and HP-GL?

Developed by Hewlett-Packard, HP-GL/2 and its predecessor HP-GL are standard formats for plotters and were defined along with the first plotters. These formats were conceived for the needs of the CAD world and are constantly updated. HP-GL/2 has been the plot standard for more than 9 years. HP-GL/2 is the successor of the old-fashioned and restricted HP-GL formats. HP-GL/2 processes expanded vector and raster information using very little memory space. HP-GL/2 is a 1:1 display of a plot; plot information is in HP-GL/2. Every CAD system can create HP-GL/2, as its goal is a technical drawing in the form of a plot. According to the distribution any CAD system supports HP plotter drivers.

HP-RTL supports Raster Graphics in HP-GL/2

The HP-RTL format for the interpretation of raster information is integrated into the HP-GL/2. These two formats (HP-GL/2 is HP-RTL) enable the saving of hybrid-data, i.e. vector and raster information are saved in the same format. Vector information is saved as HP-GL/2, raster information a HP-RTL. Usually the format is defined as HP-GL/2 and has the file ending *.PLT. The HP-RTL within the HP-GL/2 is not mentioned.

HP-GL was founded with the first Plotters

Together with the first plotters the HP-GL format was defined. There are many different versions. The HP-GL is old-fashioned and was replaced by HP-GL/2 in 1990 and should not be used for new applications. It does not support raster information.

Which HP-GL/2 and HP-GL Files can be opened?

As a general rule, any HP-GL/2 and HP-GL file of any CAD system can be read, processed and exported. There are many plot file-viewing programs available on the Internet. Examples: Autovue, Normica view. If you have created a HP-GL/2 file, which cannot be displayed correctly, verify whether the file was created with the correct assignments.

Benefits of using HP-GL/2

‘HP-GL/2 is standard:’ Any CAD system can create HP-GL/2, as the purpose of a CAD system is a technical drawing in the form of a plot. According to distribution any CAD system supports HP’s plotter drivers.
HP-GL/2 is precise: This format was conceived mainly for CAD applications and therefore it possesses the accurateness necessary for CAD.
HP-GL/2 is a multi-talent: HP-GL/2 processes vector information just as raster information. Within HP-GL/2 the format HP-RTL is integrated for raster interpretation. The definition of extended vector features is possible, too, such as influencing line-end and line-join, etc.
HP-GL/2 has a structure: In HP-GL/2 the pen assignments are saved clearly, and arranged according to the plot pen scheme. This is well known by any CAD user and offers a very good structure for clarity of the drawing. This clarity and standard naming makes the exchange of information easy.
HP-GL/2 needs very little memory space: In this format the vector and raster information are saved in an extremely compressed form (The raster information for example are internally put through up to eight compressors, which is possible to save and restore the data without loss). None of the usual hybrid formats (meta files, which process vectors as well as bitmaps) offer a similarly efficient compression.

Disadvantages of using HP-GL/2

PDF / Postscript format is industry standard: Adobes PDF standard is now the industry standard for sharing “print ready” information between persons. R.I.P. HP-GL/2.