The electronic absorption line shape of a model chromophore at liquid interfaces is numerically evaluated using electrostatic continuum theory. The interface is described as a sharp boundary separating two bulk media, each characterized by different optical and static dielectric constant. The chromophore is modeled as a pair of spherical cavities in which two equal and opposite point charges are embedded, but more complicated charge distributions are possible. All possible orientations of the two cavities relative to the interface are properly weighted, including the cases where each cavity may be located in both phases. Comparisons are made with experiments, approximate analytical results, and molecular dynamics simulations.