IWCIA’20 is the twentieth of a series of International Workshop on Combinatorial Image Analysis. Image analysis is a scientific discipline providing theoretical foundations and methods for solving problems appearing in a wide range of areas, as diverse as medicine, robotics, defense, and security. As a rule, the processed data are discrete; therefore, the “discrete approach” to image analysis appears to be a natural one and has an increasing importance. It is based on studying combinatorial properties of the considered digital data sets. Combinatorial image analysis often features various advantages (in terms of efficiency and accuracy) over the more traditional approaches based on continuous models requiring numeric computation