1. A method of verifying the presence and the placement of sub-resolution assist features (SRAFs) in a photomask layout of an integrated circuit (IC) chip design, comprising the steps of: determining selected optical image properties of main features of a sample layout in the presence or absence of SRAFs; analyzing the optical image properties of the main features to establish a criterion for subsequent placement of SRAFs in the photomask layout of the IC chip design; performing a simulation on the complete photomask layout of the IC chip design with SRAFs; sorting the photomask layout geometry based on predetermined categories; and based on the established criterion, identifying regions of the photomask layout lacking adequate placement of the SRAFs, and correcting the inadequate placement of the SRAFs.