Xerox 4890 Advanced Product Reference - page 11

LPS FUNDAMENTALS

Custom software applications may be modified to support

highlight color by coding in routines that can add enhanced

DJDEs and metacodes to the data stream. 

Adding color after document creation

If the platform in use supports applications producing line printer

or LCDS data streams, it is possible to produce highlight color

documents even in the absence of a color document creation

package.  Black-only line printer or LCDS data streams produced

during document creation may be modified to print in highlight

color.

If an application does not support color, color may be added to

a document by modifying the job source library (JSL) for the

application.  Copy modification entries (CMEs) are used to apply

static color to the variable data in a document.  If the application

uses a font index byte to change fonts, that byte can also be

used as an ink index to change text color when the font is

changed.

Adding color to Interpress and PostScript data streams

With application packages producing Interpress and PostScript

data streams, color is added to black-only documents at the

printer using the ink substitution command.  By substituting the

highlight primary color for black, you can change a black-only

page or report to a color page or report.  The color report uses

only the pure primary color plus tints of that color.  

If both black and color dry ink are required in an Interpress or

PostScript document, the color data stream must be generated

on the host or workstation.  These documents must be created

using a color application package. 

Translating from a full color palette to highlight color

Full color software applications are based on a parametric color

model such as Red-Green-Blue (RGB), rather than on a highlight

color model.  These full color models produce a larger range of

colors than are available on the 4890.  Therefore, a translation or

mapping must be made between the colors used in the

application and the colors available on the printer.

In the case of Interpress documents, the mapping is done on the

printer by the Interpress decomposer.  The decomposer uses a

4890 resident software task called ICS ink catalog search (ICS)

that finds the ink that most closely approximates each color

referenced in the Interpress document.  

Application colors are mapped to the highlight color ink closest

in value; dark colors are mapped to shades and dark tones of the

highlight primary, while light colors are mapped to tints or light

tones.  The highlight hue is preserved; for example, if the printer

is loaded with blue dry ink, the mapping is to the blue palette.

In this instance, reds are mapped to grays, not to blues.

In the case of PostScript documents, the mapping of full color to

highlight color is provided by the PostScript interpreter in the

Entire FIBRE 400/600 front end.  The output of the Entire FIBRE is

XEROX 4890 HIGHLIGHT COLOR LPS PRODUCT REFERENCE

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