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Compensation for Secondary-Color Spot Size in Ink-Jet Printing

IP.com Disclosure Number: IPCOM000039282D
Original Publication Date: 1987-May-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 3 page(s) / 43K

Publishing Venue

IBM

Related People

Palmer, DR: AUTHOR

Abstract

A method is disclosed for compensating for the difference in spot size between primary and secondary colors by increasing the line weight of primary color characters to more closely approximate the weight of the secondary color characters. By implementing this algorithm in realtime as the character columns are printed, storage for the compensated font (Image Omitted) is not needed. In addition, the algorithm will operate on any font available to the printer. The algorithm is simple enough to have little or no effect on printer throughput or microcode size. Many ink-jet printers provide inks for only the primary subtractive colors (cyan, magenta, and yellow). Secondary subtractive colors (red, green, and blue) are created by printing two primary colors in the same place on the page.

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Compensation for Secondary-Color Spot Size in Ink-Jet Printing

A method is disclosed for compensating for the difference in spot size between primary and secondary colors by increasing the line weight of primary color characters to more closely approximate the weight of the secondary color characters. By implementing this algorithm in realtime as the character columns are printed, storage for the compensated font

(Image Omitted)

is not needed. In addition, the algorithm will operate on any font available to the printer. The algorithm is simple enough to have little or no effect on printer throughput or microcode size. Many ink-jet printers provide inks for only the primary subtractive colors (cyan, magenta, and yellow). Secondary subtractive colors (red, green, and blue) are created by printing two primary colors in the same place on the page. This allows six colors to be printed with only three ink supplies. Secondary color dots created in this manner, however, have a larger spot size than primary color dots since more ink is deposited in the same area. Text printed in a secondary color therefore appears bolder than the same text printed in a primary color because of the larger dots. The disclosed method minimizes this difference so that characters appear to have the same line weight independent from their color. This is accomplished with almost no reduction in printer throughput and little increase in the size of the printer control program. No increase in font storage size is required and the method can be applied to all printer fonts including fonts downloaded from the host computer. Each text character is stored in the printer as a matrix of dots, as shown in Fig. 1. A set of compensated characters is derived from the original set by shifting each matrix one column to the right and...