1. A computer method for generating a pixel display pattern from a pixel given pattern using a nonlinear continuous transform from given pixel values to generated pixel values, the method comprising: (a) for at least one display attribute, determining for each one of the given pixel values, via a processor, constraints which include an upper bound and a lower bound on the slope of the transform at each respective one of the given pixel values, wherein each lower bound is greater than 0, and wherein the constraints for at least one of the given pixel values differ from the constraints for at least one other of the given pixel values; and (b) for a background having a background luminance value and subject to the said constraints, determining the transform via the processor such that, if the pixel display pattern is displayed against the background, visual distortion as compared with the pixel given pattern is minimized.