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.
A bitmap that is stored in compressed form using the RLE algorithm. SGI chromaticity ranges from 8 to 32 bits/pixel. The format is designed for use on Silicon Graphics workstations. It is also known as Irix RGB or IRIS.