Convert HPGL to PGM

The HPGL file extension, short for Hewlett-Packard Graphics Language, is a file format and printer control language developed by Hewlett-Packard in 1977 for use with their plotter printers, starting with the HP-9872. HPGL files contain commands that instruct plotters to draw images using lines rather than dots, making them essential in CAD applications and technical drawings. The language uses a series of two-letter codes followed by parameters to control the plotter's actions, such as moving the pen or drawing shapes.

The Portable Graymap (PGM) file extension, originating in the late 1980s as part of the Netpbm project, stands for "Portable Gray Map". It serves as a simple, versatile format for grayscale images, enabling easy reading and writing by various programs. Due to its straightforward structure and plain text encoding, it's often used in academic and research settings where ease of parsing and accessibility are crucial. PGM files store grayscale images in a compact, efficient manner, making them an essential tool for image processing tasks.