REDUCING HALFTONE PICTURES

Abstract

This paper addresses the problem of scaling pictures, presented either in greyscale or bilevel form, into a bilevel representation suitable for reproduction on a bitmapped display or printer. It shows how the scaling and halftoning processes can be combined into one, which integrates locally using a given interpolation function and follows a Peano scan to avoid moire artifacts. This technique accomplishes reduction by arbitrary scale factors (which need not be the same in x and y). A major result is that reduction from a bilevel representation produced by the Peano scan technique is not significantly inferior, in terms of the perceptual result, than scaling from a greyscale original.