We propose an inversion calculation method based on a simple "pixel-flipping" approach. The simple method features innovative wavefront-expansion and wavefront-based damping techniques in order to obtain accentuated corrections near the drawn pattern. The method is first employed to be a stand-alone optical proximity correction solution that directly calculates the corrected masks with acceptable contours and image contrast. In addition, a model-based pre-OPC flow, where the initial sizing of drawn patterns and surrounding sub-resolution assist features (SRAF) are simultaneously generated in a single iteration using this inversion calculation is also proposed to minimize technology-transition risks and costs. A mask simplification technique based on the central moments is introduced in order to snap the corrections into 45 degree and axis-aligned line segments. This approach allows achieving optimized corrections while minimizing the impact to the existing and validated correction flow.