The added functionality such as contour tracking and corner detection which logic programming lends to standard image operators is described. An environment for implementing low-level imaging operations with Prolog predicates is considered. Within this environment, higher-level image predicates (contour tracking and corner detection) are constructed. The emphasis is not on building better corner detectors, but on presenting ways of using the unification and backtracking features of logic programming for these tasks. The performance of this implementation of contour tracking and corner detection has been very good in many more complex images, as it allows for feedback both ways between sensor input and symbolic models. More important is the parameter selection capability in a dynamic version where background properties change. The authors present examples of Prolog predicates for performing the contour and corner detection operations.>