Files with the PI1 extension were used by an application running on Atari computers called Degas & Degas Elite. It is an older uncompressed format for storing bitmap graphics. It is characterized by a palette of 16 colors and a resolution of 320x200 pixels.

PI1 files can be supported by currently used programs, but this format is rarely used and is considered obsolete. Atari computers were popular in the 70's and 80's of the 20th century.