Digital Parallelism, Perpendicularity, and Rectangles
Ravinder Krishnaswamy, Chul E. Kim · IEEE Transactions on Pattern Analysis and Machine Intelligence · 1987
The slope of digital line segments is defined and an algorithm to evaluate it is presented. Parallelism and perpendicularity of two digital line segments are also defined. Finally, rectangular digital regions are defined and characterized, and an algorithm that determines whether or not a given digital region is a digital rectangle is presented.