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
1-5
