1. A non-transitory computer readable medium storing instructions that, when executed on a computer system, cause the computer system to carry out a method for converting a pixelized image of an e-beam exposure for a mask to a different resolution pseudoimage suitable for photolithography simulation while preserving a shape of a contour line defined by a threshold value for the e-beam exposure, the method comprising: receiving a first pixelized image of an e-beam exposure for a mask having a plurality of first pixels, the first pixels defining a contour line for the e-beam exposure based on first pixel values in relation to an e-beam threshold value; generating a second pixelized image from the first pixelized image, the second pixelized image having a plurality of second pixels with a different resolution than the plurality of first pixels, the step of generating comprising: dividing the first pixelized image into regions of values, the values determined from the first pixel values; for each region, determining a contribution of the region to the second pixel values in the second pixelized image, wherein the contribution is selected from a set of predetermined contributions that are a nonlinear function of the values in the region, the nonlinear function relating to the threshold value and the contour line, the selection based at least in part on the values in the region; and accumulating the contributions of the regions to generate the second pixelized image, the second pixelized image suitable for photolithography simulation.