DataGlyph
From Just Solve the File Format Problem
DataGlyph is a proprietary bar code technology created at Xerox PARC and covered by US Patent 6,641,053. It encodes data by lines leaning in one of two directions, which correspond to zero or one bits in the data being encoded. The resulting pattern of lines can be concealed in an image so that it doesn't obviously look like a bar code of any sort (this sort of hidden data is known as steganography).
