 He invented the per-scanline variable pre-filtering compression method used by PNG, the sum-of-abs heuristic used by many encoding programs, and proposed an early version of the Adam7 algorithm, using 5 passes rather than 7.In 1998, he was one of the 23 original creators of the "Transhumanist Declaration".As of 1999, he was a member of the Extropians futurist society.