As semiconductor technologies move toward 70nm generation and below, contact-hole is one of the most challenging features to print on wafer. There are two principle difficulties in defining small contact-hole patterns on wafer. One is insufficient process margin besides poor resolution compared with line-space pattern. The other is that contact-hole should be made through pitches and random contact-hole pattern should be fabricated from time to time. PIXBAR technology is the candidate which can help improve the process margin for random contact-holes. The PIXBAR technology lithography attempts to synthesize the input mask which leads to the desired output wafer pattern by inverting the forward model from mask to wafer. This paper will use the pixel-based mask representation, a continuous function formulation, and gradient-based interactive optimization techniques to solve the problem. The result of PIXBAR method helps gain improvement in process window with a short learning cycle in contact-hole pattern assist-feature testing.