System and Method for Dynamically Shifting Error Diffusion Data

Abstract

Error diffusion is performed using a Floyd-Steinberg-like approach. A integer-representation of a running error is compressed by storing only its most significant bits and returning any remainder to the error diffusion processor. The running error is shifted to the right until only the desired number of significant bits remain, and this compressed error is stored. Any portion of the original running error that is lost due to the shifting is treated as a remainder and is returned to the error diffusion processor for use in calculating an adjusted current pixel value. The amount of the shift is retained in compressed form to keep track of the number of shifts needed to form a truncated running error from the compressed running error.

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       22 . An error diffusion system for halftoning image data pixels one image line at a time, the system configured to calculate an adjusted pixel value for a current pixel in a current image line, the adjusted pixel value including partial errors from pixels on a previous image line, wherein the partial errors from the pixels on the previous image line are calculated only after halftoning of the entire previous line has been completed. 
   
   
       23 . The error diffusion system according to  claim 22 , wherein the partial errors from the pixels on the previous image line are calculated only after halftoning of the immediately preceding pixel on the current image line has been completed. 
   
   
       24 . The error diffusion system according to  claim 22 , wherein the partial errors from the pixels on the previous image line are calculated only after decompressing a compressed running error corresponding to a pixel on the previous image line.