Source : Free On-Line Dictionary of Computing

Adam7
     
         One of the {progressive coding} methods
        used in {PNG} {images}.  Adam7, named after its author, Adam
        M. Costello, consists of seven distinct passes over the image.
        Each pass transmits a subset of the {pixels} in the image.
        The pass in which each pixel is transmitted is defined by
        replicating the following 8-by-8 pattern over the entire
        image, starting at the top left:
     
         1 6 4 6 2 6 4 6
         7 7 7 7 7 7 7 7
         5 6 5 6 5 6 5 6
         7 7 7 7 7 7 7 7
         3 6 4 6 3 6 4 6
         7 7 7 7 7 7 7 7
         5 6 5 6 5 6 5 6
         7 7 7 7 7 7 7 7
     
        (2000-09-12)