The characterization of lattices or foams may require to build a geometric and mechanical model for each specific sample. A method to build an explicit analysis-suitable B-Spline beam model directly from digital images is presented. More precisely, we present an extension of the Virtual Image Correlation method to the case of multiple interconnected beams with variable cross-sections. The performance of the method is demonstrated through a series of examples involving synthetic and real images of lattice and more general cellular materials.