Joan L. Mitchell

Joan Laverne Mitchell (1947 to 2015) was an American computer scientist, data compression pioneer and inventor who, as a researcher at IBM, co-invented the JPEG digital image format. Born in Modesto, California, she took a physics degree at Stanford University in 1969, then a master's degree in 1971 and a doctorate in 1974 in condensed matter physics at the University of Illinois at Urbana-Champaign, where she learned to program so that a computer could solve the equations of her research. She began work at the IBM Thomas J. Watson Research Center in 1974, and her inventions there included a method for ultrasonic printing, thermal-transfer printing later used in some models of the IBM Selectric typewriter, data compression for fax machines, a teleconferencing system and the Q-coder method of arithmetic coding used in JBIG image compression. From 1987 to 1994 she helped develop the JPEG standard and wrote the first book on it with Bill Pennebaker. She became an IEEE Fellow in 1999, an IBM Fellow in 2001 and a member of the National Academy of Engineering in 2004, and she retired in 2009 from InfoPrint Solutions.