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: detecting, by the computing device, an artifact in a digital image, where the detecting comprises partitioning the digital image into overlapping regions; and removing, by the computing device from the digital image, the detected 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.