System and memory-buffer management method for reducing random access memory requirements in error diffusion halftone applications

Abstract

An error diffusion halftoning system and a method of managing halftoning errors utilize a quantization technique to reduce the required size of a primary error buffer that is needed to diffuse the halftoning errors. By implementing the quantization technique, the primary error buffer can be reduced from an 8-bits-per-bin error buffer to a 2-bits-per-bin error buffer for 256 grayscale. The reduction in bin size decreases the cost of the primary error buffer and, consequently, the cost of an error diffusion halftoning (EDH) device of the system that generates halftone values from grayscale values of a digital image. The quantization technique is executed on cumulated half-toning errors, derived from apportioned halftoning errors associated with previously processed pixels. In addition, the system and method utilize an error diffusion procedure to diffuse quantization errors that are produced from the execution of the quantization technique. In one embodiment, entire quantization errors are sequentially transmitted to a supplemental error diffuser, so that each quantization error can be introduced to the grayscale value of the next pixel to be processed. In another embodiment, the quantization errors are apportioned using predefined multiplicative parameters and eventually diffused to two or more unprocessed pixels that are adjacent to the pixel currently being processed.