1. A system comprising a computing device and at least one program module that are together configured for performing actions, the computing device including at least one processor and memory, the actions comprising: removing, by the computing device from a digital image, an artifact that results from a physical impurity, where the removing is based on projection characteristics of the physical impurity and on correlations in colors identified in the physical impurity, and where the removing results in an impurity-free appearance in the digital image.