This is a format created in the Acorn Draw program, intended for image visualization by using vector lines. It’s used for storing information in the publishing business (brochures, logotypes, etc.). The main advantage is it’s high quality source images when printing. It’s been in use since 1980.
It is used as a common format for bitmaps in operating systems environments based on the UNIX kernel. It is designed for use in many types of graphics. It can be used for all kinds of data with two-dimensional arrays. It covers the RGB-space and transparency levels.