Discrete geometry and Azriel Rosenfeld

Professor Azriel Rosenfeld did important work in several areas of Image Processing, Pattern Recognition and Computer Vision. I had the good fortune to interact with him on several topics for over 30 years and it is difficult to select a single topic to cover in a short paper. I settled on digital geometry because both our first and last contact dealt with this area. Furthermore Azriel not only did pioneering work on digital geometry, he also continued research on the topic for the rest of his life. Instead of trying to write something on a specific sub-topic of digital geometry, I opted to discuss why the area is so challenging.