Ronald J Vaughn

US Patent:

54758009, Dec 12, 1995

Filed:

Sep 30, 1992

Appl. No.:

7/954787

Inventors:

Ronald J. Vaughn - Fort Collins CO
John R. Matthews - Vancouver WA

Assignee:

Hewlett-Packard Company - Palo Alto CA

International Classification:

B41J 221
H04N 146

US Classification:

395109

Abstract:

In liquid-ink color graphics printing, true black ink is preferred over composite black wherever possible, but poor print quality results from printing black ink too close to color ink, due to limitations in present ink chemistry. A method of processing color bit-map graphics data in a four-color liquid-ink printing system, so as to maximize use of black ink while maintaining a minimum spacing between black and color inks is disclosed. The input data is stored in CMY bit-map color planes. Preliminarily, data representing composite black is moved from the color planes into a K plane for printing by a true black pen. The data is examined to detect any black ink within the minimum spacing from color ink. The examination is expedited by partitioning the data into blocks, and indicating each block as a color block, a black block, or a white block. These indications are conveniently stored in a color table and a black table, in which each block of data is represented by a single bit.