What Is an HPGL File?

This article describes what an HPGL file is and how to open one or convert one to a different file format, like PDF, DXF, DWF, etc.

What Is an HPGL File?

A file with the HPGL file extension is an HP Graphics Language file that sends printing instructions to plotter printers. Unlike other printers that use dots to create images, symbols, text, etc., a plotter printer uses the information from the HPGL file to draw lines on the paper.

How to Open an HPGL File

To see the image that would be created on the plotter, you can open HPGL files for free with XnView or HPGL Viewer.

You can also read HPGL files with Corel's PaintShop Pro, ABViewer, CADintosh, and ArtSoft Mach. Considering how common these files are for plotters, the HPGL format is probably supported in most similar tools.

Since they're text-only files, you can also open one using a text editor. Notepad++ and Windows Notepad are two free options, but there are other free text editors. Opening the file this way will let you change and view the instructions that make up the file, but won't translate the commands to an image...you'll just see the letters and numbers that make up the file.

How to Convert an HPGL File

HPGL2 to DXF is one free program for Windows that can convert HPGL to DXF, an AutoCAD image format. If that tool doesn't work, you can do the same with the demo version of HP2DXF.

Very similar to those two programs is ViewCompanion. It's free for 30 days and also supports converting to DWF, TIF, and some other formats.

The HPGL Viewer program mentioned can also save the file to JPG, PNG, GIF, or TIF.

hp2xx is a free tool to convert HPGL files to graphics formats on Linux.

You can convert an HPGL file to PDF and other similar formats using CoolUtils.com, a free file converter that runs in your browser, which means you don't have to download the converter to use it.

More Information on HPGL Files

HPGL files describe an image to a plotter printer by using letter codes and numbers. Here's an example of one that describes how the printer should draw an arc:

 AA100,100,50;

AA means Arc Absolute, meaning these characters will build an arc. The center of the arc is described as 100, 100 and the starting angle is defined as 50 degrees. When sent to the plotter, the HPGL file will have told the printer how to draw the shape using nothing but these letters and numbers.

Other commands exist to do things like draw a label, define the line thickness, and set the character width and height. Others can be seen in this HP-GL Reference Guide.

Instructions for line width don't exist with the original HP-GL language, but they do for HP-GL/2, the second version of the printer language.

Still Can't Open the File?

If your file won't open at this point, after trying the suggestions above, there's a good chance you're misreading the file extension. Some file extensions look really similar even though the formats are completely different, meaning you'll need a different program to open the file.

LGP is one example. While it does share three of the four file extension letters in HPGL, they're really archive files used by Final Fantasy games.

HPI files are similar but they require Hemera software to view them since they're images.