DjVu (pronounced déjà vu) is a computer file format designed primarily to store scanned images, especially those containing text and line drawings.

A two-dimensional image coding specification using compression techniques.

Portable Network Graphics.

An X-Face is a small bitmap (48 × 48 pixels, black and white) image which is added to a Usenet posting or e-mail message, typically showing a picture of the author's face. The image data is included in the posting as encoded text, and attached with an 'X-Face' header.