This paper describes an infrastructure that enables transparent development of image processing software for parallel computers. The infrastructure's main component is an image-processing library containing operations capable of running on distributed memory MIMD-style parallel hardware. Since the library has a programming interface identical to that of a familiar sequential image-processing library, the parallelism is completely hidden from the user. All library functions are based on an abstract parallel image-processing machine (APIPM), introduced in this paper. To guide the process of automatic parallelization and optimization, a performance model is defined for operations implemented using APIPM instructions. Experiments show that for realistic image operations performance predictions are highly accurate. These results suggest that the infrastructure's core forms a powerful basis for automatic parallelization and optimization of complete applications.