XBM
From Just Solve the File Format Problem
XBM (X BitMap) is a file format for bi-level raster images. It was one of the few image formats supported by early graphical web browsers.
An XBM file is plain text, and doubles as a fragment of C programming code. The format is very inefficient in size, but it can be useful as a simple way to embed an image into a C program.
See also
Sample files
- http://www.fileformat.info/format/xbm/sample/index.htm
- http://people.sc.fsu.edu/~jburkardt/data/xbm/xbm.html