A vector images format for the HP plotter, created with the help of the Hewlett-Packard Graphics language. It consists of a set of two-character encoding which determines the allocation of starting points in the plotter. It’s used in various programs for plotting and it’s scalable, maintaining image quality. It has an ASCII structure and is an equivalent to HPG files.
This format has the same color structure as RGB, but it includes an alpha channel that is used to display various levels of transparency. The transparency value is set from 0 to 1, where 1 corresponds to opacity. It is described using the CSS3 programming language.