bi-level image
A bi-level image is a computer image in which each pixel (picture element) is represented by only one bit, which can be either on or off. For this reason, a bi-level image contains only two colors: a background color and a foreground color. Bi-level images are typically created as the result of scanning a printed image with a scanner that can only register light or dark or for the purpose of facsimile transmission.
JBIG provides standards for the compression of a bi-level image.