[54] TABLE BASED FAST ERROR DIFFUSION HALFTONING TECHNIQUE
[75] Inventors: Kevin R. Hudson, Vancouver; Thomas B Pritchard, Prairie, both of Wash.
[73] Assignee: Hewlett-Packard Company, Palo Alto, Calif.
[21] Appl. No.: 08/961,047 [22] Filed: Oct. 30, 1997
[51] Int. CI. II04N 1/46
[52] U.S. CI 358/1.9; 358/502
[58] Field of Search 395/109; 382/251-252,
382/162, 167; 358/502, 1.9, 518, 523
[56] References Cited
U.S. PATENT DOCUMENTS
3,916,096 10/1975 Everett et al 178/6.6 R
4,339,774 7/1982 Temple 358/283
4,891,714 1/1990 Klees 358/456
5,018,008 5/1991 Asada 358/518
5,107,332 4/1992 Chan 358/80
5,313,287 5/1994 Barton 358/458
5,375,002 12/1994 Kim et al 358/521
5,444,461 8/1995 Oz et al 345/154
5,623,281 4/1997 Markandey et al 345/108
5,676,716 10/1997 Shu 358/518
5,761,394 6/1998 Sugiura et al 382/162
5,867,599 2/1999 Michealis et al 282/237
OTHER PUBLICATIONS
Hewlett-Packard Patent Application 08/812,777, 3/06/97, Fast Error Diffusion Alogrithm.
Hewlett-Packard Patent Application 08/880,475, 6/23/97 Correlating and Magenta Planes For Error Diffusion Halftoning.
Primary Examiner—-Thomas D. Lef
Assistant Examiner—Stephen Brinich
[57] ABSTRACT
In an error diffusion process for an inkjet printer, a look-up table is indexed by an input color tone, with entries for base output level, base level error term, threshold error term, and whatever other data may be relevant. This table may be embodied in a conventional memory or software code. The base output level corresponds to the number of ink drops to be ejected by the inkjet print for particular ink colors, the base level error term reflects the error between the input and output of the look-up table, and the threshold error term is subtracted from the total error for the pixel if the base output level is incremented by one.
34 Claims, 6 Drawing Sheets
