Coauthor of PNG spec, developer/maintainer of libpng, on development teams for ImageMagick and GraphicsMagick. Author of pngcrush. Maintains PNG support in Firefox. Retired, father of four, grandfather of fifteen.
After a little googling, I was saddened to find that Glenn passed away 2 years ago.
Thank you Glenn for your work on PNG - a vital part of the web as used by literally billions.
Thank you also for your .SE contributions, including those to codegolf. In the few interactions I had with Glenn, he was a real gentleman, greatly knowledgeable and always helpful.