Handheld Reflectance Acquisition of Paintings

Relightable photographs are alternatives to traditional photographs as they provide a richer viewing experience. However, the complex acquisition systems of existing techniques have restricted its usage to specialized setups. We introduce an easy-to-use and affordable solution for using smartphones to acquire the reflectance of paintings and similar almost-planar objects like tablets, engravings and textile. Our goal is to enable interactive relighting of such artifacts by everyone. In our approach, we nonuniformly sample the reflectance functions by moving the LED light of a smartphone, and simultaneously, tracking the position of the smartphone by using its camera. We then propose a compressive-sensing-based approach for reconstructing the light transport matrix from the nonuniformly sampled data. As shown with experiments, we accurately reconstruct the light transport matrix that can then be used to create relightable photographs.