1. A computer-implemented method for determining a disposition of a possible defect in a photo-mask, comprising: receiving a first image of a first region around the possible defect in the photo-mask, wherein the photo-mask corresponds to a target mask pattern; generating, via the computer, a second image based on the first image to extend the field of view of a measurement device that acquired the first image, wherein the second image includes the first region and a second region surrounding the first region, and wherein the second region is based on the target mask pattern; calculating a simulated mask pattern based on the second image using an inverse optical calculation in which the second image is at an image plane in a model of an optical system and the simulated mask pattern is at an object plane in the model of the optical system, wherein the second region in the second image reduces optical proximity effects in the simulated mask pattern associated with a boundary of the first region; simulating a wafer pattern in a photo-lithographic process based on the simulated mask pattern; and determining the disposition of the possible defect based on the simulated wafer pattern and a target wafer pattern.