This invention is a method of multilevel dither screening in a printer. Plural
pixel values are packed into equal sections of a first data word. Corresponding
dither values are packed into the equal sections of a second data word. These first
and second data words are added in an arithmetic logic unit selectively spilt into
the equal sections. Each section of the sum data word is saturated to all 1's.
A predetermined number of least significant bits of the saturated sections are
truncated. The resulting normalized pixel values are quantized into a limited set
of threshold ranges. This dithering process serves to introduce an amount of scattering
to the input pixel values to reduce quantization and pixelation artifacts in the
final printed product.