HP (Hewlett-Packard) PCL 5 User Manual

PCL 5 Color Technical Reference Manual

Edition 1 E00994

5961-0635 Printed in U.S.A. 9/94

Notice

The information contain ed in thi s documen t is subject to change witho ut n otic e. HEWLETT-PACKARD MAKE S NO WARRANTY OF ANY KIND WITH REGARD T O

THIS MA T ERIAL, INCLUD ING , BUT NOT LIMIT ED TO, TH E IMPL IED WARRANTIES OF MERCHANTABILITY AND FIT NESS FOR A PARTICULAR P URPOSE. HewlettPackard shall not be liable for er rors co ntain ed herein or for incide ntal c on seque ntial d amages in connection with the fur nish in g, per for man ce, or use of this material.

This document con tains pr opr ietar y inf or mation whic h is protec ted by copy rig ht. All righ t s are reserved. No part of th i s documen t may be photoc opied, reproduc ed, or translated w ithout the prior written consent of Hewlett-Packard Company.

Adobe, PostScript, and the PostScript logo are trademarks of Ado be Systems Inco rp orated which may be registered in certain jurisdictions. AppleTalk is a registered trademark of Apple Computer, Inc. PCL and Resolution Enhancement are registered tr ademar ks of Hewlett-Pac kar d Company. IBM is a registered trademark of International Business Machines Corporation.

First Edition — Septembe r 1994

iiii

Inside This Manual

What You Can

Learn

From This Manual

Note All commands describe d in this manual are not nece ssarily

Manual Organization

This manual describes the PCL 5 commands used to print color on the HP Color LaserJe t and Desk Jet 1200C printers. Some of the main topic s include an overview of the color printing process, using palettes, choosing color modes, adjusting outpu t color to meet your requir eme nts, printing color raster graph ics, and HP-GL /2 ve cto r graphics. Ex amples are prov ided which demon str ate the use of the PCL 5 color commands.

supported by both printe rs. See the PCL 5 Comparison Guide for feature support inf ormation for eac h prin ter.

This manual is written primarily for users that are already familiar with PCL 5 printe r featur es. For infor mation on using PCL 5, see the PCL 5 Printer Language Technical Reference Manual.

This manual contain s seve n chapter s. A brief description of each chapter is prov ided below.

Chapter 1. C olo r Pr in ting Ov er vie w

This chapter explains back gro und in for mation about prin ting color docume nts usin g PCL 5. Topics include palettes, device-d epen de nt v s. device -in depe ndent color, color selection, pixel encodin g, color modes, and c olor matchin g.

Chapter 2. Us in g Co lo r Mo des

Chapter 2 defines th e four color modes and desc r ibes how to use them, including descrip tion s of sen ding color raster data using different pixel encoding modes and color spaces.

iiiiii

Chapter 3. Us ing Pal ett es

This chapter descr ibes the palettes associated with the four color modes and explains how palettes are created, saved, and modified.

Chapter 4. Modifying Output Color

This chapter explains ho w color can be optimized by co mpensating for differe nt con dition s, such as variation s in color due to light sou rces, limitations of the orig inal ar twork and variation s in viewin g monitor s. Th e chapter details the use of halftone rendering algorithms, color lookup tables, gamma correction , and viewing illumin an t commands provide d so that user s can requ est and rece ive colored outpu t that match es the ir expec tation s.

Chapter 5. The PCL Print Model

Chapter 5 describes the pr int mode l and how it deter min es the printed outcome w he n vario us patter ns, colo rs, and images are applied together on a page. This chapter di scus ses the role that logical operation s and transparenc y mode s have on this process.

Chapter 6. Ra ste r Gr ap hi cs

This chapter descr ibes the raster graph ics co mmand s and also compressing raster graphics images using various compression methods.

iviv

Chapter 7. C olo r Vector Graphi cs (H P-G L/2 )

This chapter di scu s ses pr in ting color pag es using HP-GL/ 2, the vector graphic s lan guag e inclu de d on all PCL 5 printers. The chapter desc ribes new and/or mod ified HP-GL/2 commands and how they are used to prin t with HP color printer s.

Index

This manual includes an index for quick access to PCL command information.

Related Documents

The following documents provide related information about Hewlett-Pac kar d PCL 5 prin ter s.

PCL 5 Printer La ngua ge Technical Reference Ma nual

The PCL 5 Printer Language T echnical Reference Manual provides a description of the printer comman d langu ag e that controls PCL 5 prin ter s. Th e manual pr ov ides explanations of each PCL command, and examples demonstrating how the commands are used to manipulate the printe r. A lar ge portio n of th e manu al is devoted to HP-G L/2, the vector- b ased graph ics language in PCL 5 prin ter s.

PCL 5 Comparison Guide

This document provides printer-specific information on paper handling, internal fonts, PCL command support, and control panel in for mation . It identifies featu r e differ en ce s between the var ious PCL 5 printer s, and how the printers implement the commands describe d in the PCL 5 Printer Language Technical Refe re nc e Manual .

Printer Job Langua ge Technical Referen ce Manu al

This manual describes PJL, the HP printer job language used on many of the Hewlett-Pack ar d prin ter s. PJL is used for switching pr inter languages, r equ esting status information, changin g display messag es, in quir in g about featu r e settings, and other job-level functions.

PCL/PJL Technical Quick Re fere nce Gui de

This booklet is designed to prov ide quic k acce ss to the syntax of each PCL and PJL command. The commands are grouped by their func tion so that those familiar with PCL and/or PJL can fin d the syntax of a specific command w ithout opening the manual.

ContentsContents

1. Color Printing Overview

Color Concept s. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3

Palettes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3

Raster Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3

Raster Color vs. Non-Raster Color . . . . . . . . . . . . . . 1- 3

Device-D epen de nt vs. Devic e-I nd epen de nt Color. . . 1-3

Black and White Reference s . . . . . . . . . . . . . . . . . . . 1-4

Color Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5

Pixe l En c o ding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 -5

Color Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-7

Device-Ind epen de nt Color . . . . . . . . . . . . . . . . . . . . . . . 1- 9

Device-D epen de nt Color. . . . . . . . . . . . . . . . . . . . . . . 1- 9

Dev ic e-In d e pen de n t Color . . . . . . . . . . . . . . . . . . . . . 1 - 9

Color Matchin g. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1- 1 0

Processing Color Documen t s. . . . . . . . . . . . . . . . . . . . . 1-12

Non-Raster Color vs. Raster Color . . . . . . . . . . . . . 1-12

Color Processing Func tion s . . . . . . . . . . . . . . . . . . . 1 - 13

2. Usi n g C ol o r Mo des

Black-and- Wh ite Mod e (Defau lt) . . . . . . . . . . . . . . . . . . 2-1

Simple Color Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

PCL Imaging Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2

HP-GL/2 Imagin g Mode. . . . . . . . . . . . . . . . . . . . . . . . . . 2-2

Simple Color Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3

Contents-1Contents-1

Simple Color Command. . . . . . . . . . . . . . . . . . . . . . . 2-3

PCL Imaging Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5

Configure Image Data (CID) Command. . . . . . . . . . 2-5

Common 6-Byte Header . . . . . . . . . . . . . . . . . . . . . . 2-6

Short Form of CID Command . . . . . . . . . . . . . . . . 2-15

Long Form of CID Command . . . . . . . . . . . . . . . . . 2-17

Examples Using the CID Command. . . . . . . . . . . . 2-25

HP-GL/2 Imagin g Mode . . . . . . . . . . . . . . . . . . . . . . . . 2-28

3. Usin g Pa l ette s

Saving the Palette. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3

Push/Pop Palette Command . . . . . . . . . . . . . . . . . . . 3-3

Palette Managemen t by ID. . . . . . . . . . . . . . . . . . . . . . . 3-5

Select Palette Command . . . . . . . . . . . . . . . . . . . . . . 3-7

Palette Control ID. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-8

Palette Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-9

Simple Color Palettes . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1 1

Contents-2Contents-2

CID Color Palettes . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-13

HP-GL/2 Palettes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-15

Foreground Co l o r . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-17

Foreground Color Command. . . . . . . . . . . . . . . . . . 3-17

Programming Color Palettes . . . . . . . . . . . . . . . . . . . . 3-19

Color Component One . . . . . . . . . . . . . . . . . . . . . . . 3-19

Color Component Two . . . . . . . . . . . . . . . . . . . . . . . 3-20

Color Component Th ree. . . . . . . . . . . . . . . . . . . . . . 3-20

Assign Co l o r In d ex. . . . . . . . . . . . . . . . . . . . . . . . . . 3-2 1

4. Mo di fyi n g Ou tpu t Co l or

Halftone Ren der Algo rith m s. . . . . . . . . . . . . . . . . . . . . . 4-2

Render Alg or ithm Comman d. . . . . . . . . . . . . . . . . . . 4- 2

User-Defin ed D ithe rs. . . . . . . . . . . . . . . . . . . . . . . . . 4-5

Download Dith er Matr ix Command . . . . . . . . . . . . . 4-6

Multiple Dither Matric e s. . . . . . . . . . . . . . . . . . . . . . 4- 9

Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-10

Color Lookup Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1 1

Gamma Correction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-15

View in g Illumin ant . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-16

Mon ochro m e Printing . . . . . . . . . . . . . . . . . . . . . . . . . . 4-18

Driver Configuration Comman d. . . . . . . . . . . . . . . . . . 4- 19

5. The PCL Print Model

Command Sequence. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-6

Source T r an spare nc y Mod e Command. . . . . . . . . . . . . . 5-7

Pattern Transpar en cy Mode Comman d . . . . . . . . . . . . . 5-8

Logical Operatio ns. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-9

Logical Operations and Transparency Interactions 5-12

Logical Operation Command . . . . . . . . . . . . . . . . . . . . 5-13

T able of Logical Ope ratio ns . . . . . . . . . . . . . . . . . . . 5-1 5

Pixel Placemen t. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-21

Pixel Placemen t Command . . . . . . . . . . . . . . . . . . . 5-24

Filling with Patterns. . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2 5

Pattern ID (Area Fill ID) Command. . . . . . . . . . . . . . . 5-26

Select Current Pattern Comman d . . . . . . . . . . . . . . . . 5-30

User-Defin ed Patter n Graph ic s . . . . . . . . . . . . . . . . . . 5-31

Download Pattern Comman d . . . . . . . . . . . . . . . . . . . . 5-36

Contents-3Contents-3

Set Pattern Reference Point Comman d. . . . . . . . . . . . 5-42

Pattern Control Comman d. . . . . . . . . . . . . . . . . . . . . . 5-43

Rectangular Area Fills (Rules). . . . . . . . . . . . . . . . . . . 5-44

Pattern Tran spare nc y for Rec tan g ular Ar ea Fill. . . . . 5-49

Rectangular Fill Examples. . . . . . . . . . . . . . . . . . . . . . 5-51

6. Raster Graphics

Raster Graphics Command Sequen c e . . . . . . . . . . . . . . 6-5

Raster Graphics Resolution Command . . . . . . . . . . . . . 6-7

Raster Graphics Presen tation Mode Command . . . . . . 6-9

Source Raster Height Command . . . . . . . . . . . . . . . . . 6-12

Source Raster Width Comman d. . . . . . . . . . . . . . . . . . 6-15

Start Raster Graphics Command. . . . . . . . . . . . . . . . . 6-17

Raster Y Offset Command . . . . . . . . . . . . . . . . . . . . . . 6-19

Set Compression Method Command . . . . . . . . . . . . . . 6-20

Unencoded (Method 0). . . . . . . . . . . . . . . . . . . . . . . 6-20

Run-length En cod in g (Method 1 ) . . . . . . . . . . . . . . 6-2 1

Contents-4Contents-4

Tagged Image File Format Encoding (Method 2). . 6-21

Delta Row Compression (Metho d 3) . . . . . . . . . . . . 6-25

Adaptive Compression (Metho d 5) . . . . . . . . . . . . . 6-30

T ran sfer Raster Data Command s . . . . . . . . . . . . . . . . 6-35

End Raster Graphics Command. . . . . . . . . . . . . . . . . . 6-39

Raster Scaling. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-40

Destination Raster Width . . . . . . . . . . . . . . . . . . . . 6-41

Destination Raster Height . . . . . . . . . . . . . . . . . . . 6-41

Scale Algo rith m . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-42

Raster Graphics Example. . . . . . . . . . . . . . . . . . . . . . . 6-43

Color Raster Graphics Example. . . . . . . . . . . . . . . . . . 6-46

7. Color V e cto r Gr ap hics (HP-G L/2)

Ent er HP-GL/ 2 M o de. . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 -2

Default Settings when Enter in g HP-G L/2 . . . . . . . . 7-4

MC (Me rge C ontrol). . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7- 6

PC (Pen Color) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-14

NP (Number of Pens). . . . . . . . . . . . . . . . . . . . . . . . . . . 7-16

CR (Color Range). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7- 1 8

PP (Pixel Placemen t ). . . . . . . . . . . . . . . . . . . . . . . . . . . 7- 19

Index

Contents-5Contents-5

Color Printin g Ove r viewColor Printin g Ove r view

Introduction This chapter provides an overview of the way color i s used

in the HP Color LaserJe t and De skJet 1200C prin ter s. I t previews the remainin g chapter s, w hic h descr ibe th e specific details of Hewlett-Packard color printing.

Note The features described in this docu men t are a superset of

those supported by the Color LaserJet and DeskJet 1200C printers. Some features are supported on one or the other printer s, but not on both . See the PCL 5 Compar is on Guid e for specific feature sup port for each printer.

Processing a color document inv olves specifyin g a palette or palettes, and then using the colors within the current palette to print. For non- r aste r prin ting , items such as text, rule s, an d v ec tors are simply printed in the curren tly active color, which is specified using the For egr ou nd Color command or Select Pen command if in HP- GL /2. For ra ster printing, the color of each pixel is specified as either a direct color specific ation , or as an index into the palette, depending on the pixel en co din g mode.

The PCL Print Model deter min es how color is applied to the page. The printed re sult can vary in backgro und an d texture depending on the source transparency mode, pattern transparency mode, and selected logical operation (ROP). Besides the pr e-de fin ed shadin g and pattern s, user s can define new mono chr ome or multicolor patterns.

When printing color pages, a user can choose one of several color modes, depen din g on the desired r esults. Each color mode has a palette associated with it. Simple Color Mo de

provides a palette of fully satur ated color s wh ose colo rs are similar to those of a plotter’s pen colors. The palette is nonprogrammable, and is intended for simple printing of items such as bar and pie charts. For application s requ ir ing different or mor e specif ic c olor s, the printer offers the PCL Imaging and HP-GL/2 Imaging Mo des. The palette c olor s in these two modes can be modified to pro vid e the desir ed result.

When choosing color for a particular application, the Color LaserJet prin ter provides device-dependent and device-independent color (the DeskJet 1200C supports only device-dependent color). Device-independent color provides accurate colo r matc hing based on an absolute color standard. It is preferred w he n users wan t a prec ise co lor to match the output from ano the r devic e or to match the colo r on an existing page.

Besides providing devic e-in de pen den t co lor for prec ise colo r matching, the HP prin ter s can modify color to compen sate for various characteristics. The Color LaserJet printer supports the followin g method s of modifying color (the DeskJet 1200C printer supp or t s halfton e algorithms and gamma correction , but not colo r looku p tables or the View in g Illumin ant c omman d).

Halftone render algorithms determine how colors are rendered using the printers available colors. Halftone algorithm s can be used to chang e apparen t resolu tion , change the textu re of image s, reduc e the number of colors, and ch an ge a color image to mono chr ome.

Color lookup tables can remap colors to compensate for various diff er en ce s in inpu t data, suc h as un w anted color casts caused by unbalanced photographic light sources.

Gamma correction provides a way to adjust for color differenc es in display monitors so that the display mor e closely matches the prin ted ou tpu t.

Since the appearance of colors changes under different viewing light sources, the Viewing Illuminant command allows the application to modify outp ut color based on the light sourc e used to view the pr inte d page .

1-2 Color Printing Overview1-2 Color Printing Overview

Color Conc epts This section describes so me of the conce pts and ter mino log y

used in this chapter, such as palettes, raster vs. non-raster color, device-independent vs. device-dependent color, black and white refer en ces, co lor selection , pixel en codin g , and color modes.

Palettes A palette is a collection of colors that ar e sele cte d by their

index numbers. You can create yo ur ow n palette or choose from one of several fixed palettes. Although only one p alette is active at any time, all palettes are assigned ID numbers and can be stored in the pr inte r for later selection usin g the ID number. They can be deleted when desire d. Palettes can also be saved (pushed) to a stack and later retriev ed (popped) when needed.

Raster Mode Raster mode is entered explic itly by the Start Ra ster

command (?*r#A) or implicitly by a Transfe r Raster command (?*b#V, ?*b#W). Raster mode is exited explicitly by an End Raster command (?*rC) or implicitly by a non-raster command.

Raster Color vs.

Non-Raster Color

Device-Dependent

vs. Device-

Independent Color

Palettes are used differently dep en din g on wheth er the printer is in raster mode.

In non-raster mode, the palette is alway s used for color selection. The color of text or patter ns is specified using the Foregrou nd Color comman d ( ?*v#S).

In raster mode, the palette is only used for index ed color selection; it i s not used for direct color selection. (Indexed and direct color selection are explain ed later in this section.)

Device-dependent color spaces are relative to the dev ice ’ s ability to produce spec ific colors. For example, if red is specified in a devic e-d epen de nt color space, two differ en t printers will combin e the same amounts of cyan , mag enta, yellow, and black toner to produce the color, but the results

Color Printing Overview 1-3Color Printing Overview 1-3

will be different because of the different properties of the toner.

Device-independent color is specified absolutely, in a color coordinate system that is indep en dent of any device . For example, if red is specified in a device- ind epen de nt color space, two printers will alway s p rodu ce the same result, even though they may need to combine different amounts of cyan, magenta, y ellow, and black toner. Printer s that produce devic e-in dep en den t colo r are calibr ated to prec i se color standards.

Black and White

References

Example: Assuming the white and black refere nces are set as follows:

Device-dep endent color specific ation s are ba sed upon an arbitrary range of values for each primary color component. The range endpoints f or each color compon en t are called black and white references for that c omponent. Colors relative to these predef ine d limits are derived by specif ying the amount of each compon en t.

For the Device RGB color space, the maximum limit is called the white refer ence and the minimu m limit is called the black reference. Regardless of the number chosen, the white referenc e repr esen ts the maximu m valu e of a primary color that a device c an produ c e, and the black reference re pr esen ts the minimu m valu e of that primar y color. For example, if 100 is chosen as the white reference for red in the RGB color model, it represents the reddest red the device can pr odu ce. If 10 were chosen instead, then 10 would represent the same red.

Scenario 1

White Reference Black Reference

red = 63 red = 0 green = 63 green = 0 blue = 63 blue = 0

1-4 Color Printing Overview1-4 Color Printing Overview

Scenario 2

White Reference Black Reference

red = 63 red = 4 green = 127 green = 0 blue = 31 blue = 0

Using these referen ce values, 50% blue for scenar io 1 is 31, and 50% blue for scenario 2 is 15.

Color Selection The HP color printer s offer two methods for selecting colo rs:

Indexed selection Direct selection

In indexed selection, colors are chosen using their palette index numbers. For non-r aster mode, the palette index number is specified using the Foregro und Color command . In raster mode, the data bit combination for each pixel forms an index nu mber. The example below shows how the index numbers for an 8-colo r palette are specified:

Three-bit combinations: 0 1 0 1 0 1 0 1

0 0 1 1 0 0 1 1 0 0 0 0 1 1 1 1

Palette index number : 0 1 2 3 4 5 6 7

The number of colors in the palette dictates the numbe r of bits per pixel of raster data required to sp ecify an index number. For example, to specify 256 colors you need to send 8 bits of raster data per pixel (2

In direct selection , color s are spec ified u sing the propo rtio ns of their primary compone nts. For example, using a 24-bit-per- pixel repr esen tation , the color specified by (0xf f, 0xf0, 0x00) for red, green , and blue would pr int a sligh tly red-tinted yellow. A palette is not u sed for direc t se lec tion .

= 256).

Pixe l E nc o ding Colors are encoded in a row of raster data using either

plane or pixe l format. In planar format, all th e pixels in a row are partially specified by one plane (bit) befo re the next

Color Printing Overview 1-5Color Printing Overview 1-5

plane is sent. In pixel for mat, each pixe l is fully spec ified before sending the next pixel.

Encoding by Plane

Planar encoding uses successive data planes, each providing one bit for each pixel in a row. Each plane builds upon the prec edin g plane s until th e pixe l s in a row are fully defined. A pixel is not fully def ine d un til it has rec eiv ed a ll the planes for that r ow.

The planes in a row form index number s that defin e a pixel by selecting a palette entry. For example, an 8-entry palette requires 3 plane s (2

= 8). The underlined bits below compose the index of th e color of th e thir d pixel in the firs t row .

?*b#V row 1 plane 1 (red) b1 b1 ?*b#V plane 2 (grn) b2 b2 ?*b#W plane 3 (blue) b3 b3

b1 b1 b1 b1 . . . b2 b2 b2 b2 . . . b3 b3 b3 b3 . . .

?*b#V row 2 plane 1 (red) b1 b1 b1 b1 b1 b1 . . .

Encoding by Pixel

When encoding by pixel, each pixel is fully specified before any bits are sent for the next pixe l. For examp le, if fou r bits are needed to define a pixe l, then ever y grou p of four bits in the data stream defines a pixel. The under line d (c4 . . . c1) group below define s the secon d pix el in the first ro w.

?*b#W row 1 b4 b3 b2 b1

c4 c3 c2 c1 . . . ?*b#W row 2 b4 b3 b2 b1 . . . The table below shows the four PCL option s for selectin g

colors and encodin g color raster data.

1-6 Color Printing Overview1-6 Color Printing Overview

Indexed

Selection

Direct

Selection

Planar Encoding Pixel Enco ding

Indexed plan ar Inde xed pixe l

Direct planar Direct pixel

Color Modes There are four PCL 5 color modes:

Black and White mode Simple Color mode PCL Imaging mode HP-GL/2 Imagin g mode

All four modes create a palette. The palettes used in the Black and White mode and Simple Color mode are not modifiable. You can, however, modify the palettes in the PCL Imaging and HP-G L/2 Imaging mod es.

You can use more than one mode on the same page. For example, you could enter the Simple Color mode to print a headline and a bar chart, PCL Imag in g mode to prin t a raster photogr aph , and Black and Wh ite mode to prin t some body text. Each mode i s described in more detail in Chapter 2, “Using Color Modes.”

Device-Dependent

Color Spaces

The following PCL commands can alter color processing for device-d epen de nt c olor spaces:

Renderin g Algorithm (?*t#J) Gamma Correction (?*t#I) Color Lookup Tables (?*l#W) Configure Image Data (?*v#W) Simple Color (?*r#U) Mono chrome Print Mode (?&b#M)

Color lookup tables or gamma cor r ection (which are mutually exclu sive) can modify the mapping of inp ut to output.

Color Printing Overview 1-7Color Printing Overview 1-7

Device-Independent

Color Spaces

The following PCL commands can alter color processing for device-in de pen den t co lor spaces:

Renderin g Algorithm (?*t#J) Gamma Correction (?*t#I) Color Lookup Tables (?*l#W) Configure Image Data (?*v#W) View in g Illumin ant ( ?*i#W) Mono chrome Print Mode (?&b#M)

Device-in dependent color spaces ar e supported under the following conditions:

1. The Configure Imag e Data command (?*v#W) co nfigur es

the current palette and specifies a devic e-in de pen den t color space.

2. The Render Algorithm comman d (?*t#J) is set to one of

the following: Nearest Intensity ( ?*t0J) Device Best (?*t3J, ?*t5J) Error Diffusion (?*t4J, ?*t6J) Cluster Order ed Dith er (?*t7J, ?*t8J) Ordered Dith er (?*t1 1J, ?*t12J)

Color proces sing rever ts to de vice-dependen t pr oc essin g if the render algor ithm is chang ed from one of the above. This is because extensiv e devic e characterization is necessary to achieve device- independenc e— calibration must be based on known parameter s that aff ect the dev ic e’ s co lor gamut. Render algorithms such as Snap to Primaries (?*t1J), Snap Black to White and Colors to Black (?*t2J), or User-Defin ed Half ton e ( ?*t9J) either limit the number of colors available, or are undefin ed to the exte nt th at their performan ce i s not as precise. These algor ith ms, the refore, produce dev ic e-de pen den t re sults. D ev ice -in depe nd en t color is again generated if the render algo rith m chan g es to one of the 5 listed above and the color space has not chan ged.

1-8 Color Printing Overview1-8 Color Printing Overview

DeviceIndependent Color

The PCL language charac ter izes co lor as either devic e-d ependent or device -in depe nd en t. Both categor ies encomp a ss many color spaces, each with unique characteristics.

Device-

Dependent

Color

Device-

Independent

Color

Device-dep endent color is relative to the devic e’s inhere nt characteristics. For example, the colors produced by plotters are relative to the color of the installed plotter pens. Pen color varies consider ably, especially as pens wear out, chang in g the color of th e outp ut. Likew ise, for monitor screens, the red, g re en, and blue scr een ph osph or s determine the colo rs produ c ed. Fully satu rated co lor s can vary greatly betw een sc r een s. For p rin ter s, the color produced on a page depend s on the prin ter’s subtrac tiv e inks or toner (cyan, mag en ta, yellow, and black).

When using devic e-d epen de nt c olor, devices receiv ing relative color specific ation s for the same color freque ntly do not produce the same color. For example, a monitor’s saturated red may be differen t than a plotter’s. In short, the same color page may appear considerably different on different devices.

The HP color printer s prov ide devic e- depe nd en t color specified using either the Device RGB or CMY color spac es.

In contrast with device-dependent color, device-independent color is based on an absolute color standar d—th e tristimulus values of human vision. The device, whether a printer or other wise, is calibrated to match an indep en dent color specification. The color specification is translated in such a way that the resultant colo r is indepen den t of the device. Examples of color sp aces based on absolute standards includ e Ko dak P hoto Y CC, CIE L *a*b*, YU V, and the proposed YCr Cb. Eac h is a transfor m fr om tristimu lu s CIE XYZ space.

With proper calibration , any dev ic e can provid e a transfo rm from device-in dependent colo r spac e to the device’s ow n color space, pro du cin g outp ut fr om diffe re nt dev ic es tha t have the same color appear an c e. For example, if a monitor’s

Color Printing Overview 1-9Color Printing Overview 1-9

parameters are known (gamma, gain , chromatic ity coordinates for each primar y, and the white point), the monitor’s RGB pixel information can be transformed into device-in de pen den t co lor.

The Color LaserJe t prin ter pro vid es device- independe nt color specified usin g either the CIE L*a*b*, Color imetr ic RGB, or Luminan ce-Ch ro minan c e color spaces.

Color Matching When attempting to match color produced by differ ent

devices, it is importan t to know the differ en ce betwe en true color matching and appearance matching.

Proper devic e calibr ation can ach iev e tr ue color match in g , so that a side-by-side comparison of a prin ted pag e with the monitor on which the pag e was desig ned will show an exac t match. However, true color matching is only satisfac tor y when using the mon itor as a viewin g refer en ce. V iew ed away from the screen , the prin ted pag e may appe ar flat and unsaturated bec ause pr in ter s and monito rs hav e differ en t dynamic ranges. For example, black on the scre en appear s gray when compared to printed black, wh ich is unacceptable if the intent i s pure black . Likewise, the white produced on a monitor scr een appear s yellow or blue when compared to a white sheet of paper. True colo r matching would require that g ray be prin ted in the black area s and colored dots be printed in the white areas.

1-10 Color Printing Overview1-10 Color Printing Overview

Color Appe arance Matching

Color appearance matching goes beyond true color matching by inclu din g adju stmen ts for the dynamic range s of the devices, so the user’s inten t is maintained . For example, the white areas of a page shown on a monitor display screen would be pr inte d as white on a printed pag e because the user spec ified w hite , even thoug h the scr een cannot duplic ate a wh ite that tru ly matc hes wh ite paper. Although the prin ted color does not ex ac tly matc h scree n color, color appearanc e does match , which is what use rs usually want. To maximize user satisfaction, the PCL language uses appearan c e match in g when ren der in g device-in de pen den t co lor.

Color Lookup Tables

Color lookup tables, which prov ide addition al co ntrol of th e printed outpu t, are tran sfor mation s that map input data into a new output color range based upon poin t-by -poin t conversions.

Overhead tran sp are ncies pr ovide on e examp le of a good use for color looku p tables. Let’s say a page is printed on plain paper and it matches the user’s expectatio ns. When printing the same documen t on ov er he ad tr ansparency film, the resulting image looks unsaturated and flat. To compensate, the user can se nd a color looku p table to increase color satu ration with out ch angin g compositio n (for example, using the CIE L*a*b* color space to increase the a* and b* parameters in equal amoun ts).

Color lookup tables can al so be used to adjust data from a Kodak CD-ROM , wh ich uses th e Photo Y CC dev ic eindependen t color sp ace . The gamma correction table is complex and canno t be descr ibed by the traditio nal logarithmic expr es sion. Howev er, since the data can be mapped into new data values via tables, the user can provide a gamma correction table that e ssentially desc ribe s the complex correction factors.

Color lookup tables can be used to “ne utral-balan c e” an image. For example, an underwater photog rap h produ c es a severe bluish cast when printed. The user can eliminate that cast from the image by providin g a color looku p table that subtracts some color portion from each of the primaries.

Ill um i nation Mo d els

Illumination sources have different spectral distributions, causing colors to appear differently under one light source compared to anothe r. For example, printed colors that look normal in natural sunlig h t shift in hue when viewed u nd er fluorescen t and tun g sten ligh ting . The PCL langu ag e allows the user to compen sate for th e differ enc es in vie win g illumination using the V iew in g Illu min ant comman d. It allows the user to select differ ent illu min ation s.

Color Printing Overview 1-11Color Printing Overview 1-11

Processing Color Documents

To process a color pag e, PCL prov ides way s of specify in g and modifyin g color so that the printe d result ap pear s as the user desires. This sectio n prov ides a conc eptu al overview of the process.

Non-Raster Color

vs. Raster Color

All color portions of a page consist of eithe r:

Page Marking Primitives (non-raster data) Color Raster Data

Page Marking Primitives

Non-raster data con si sts of HP-GL/2 and PCL pag e marking primitiv es such as glyph s, rules, poly g on s, circ les, and vectors. Pag e markin g primitiv es con tain no color information about th e image. They merely mar k the pag e with attributes as signed to the curren t wo rkin g environme nt (for example, colo rs, patte rns, log ic al operation modes, etc.). Page markin g primitives act a s stencils throu g h which co lor “paint” is poured, forming a homogeneous pattern.

Page marking primitiv es prin t in the curren tly specif ied color, which is specified usin g the Foreg ro und Color command. For ex ample, if y ou specify the color blue using the Foreground Color co mmand , and then send some tex t to the printer, the text will be printed blue.

Color Ra ster Da ta

Unlike page markin g primitives, eac h pixel of a colo r ra ster image contains co lor information. A color raster pixel may be defined by either:

Palette Entry Indices Direct Color Spec ific ation s

User-def ine d color pattern s are a form of color raster, but each pixel of a user -def ine d color pattern can be defined only by palette entry indice s, not by direct co lor specification s.

1-12 Color Printing Overview1-12 Color Printing Overview

Color Processing

Functions

Given these two color uses, page mark in g primitiv es and color raster data, color processin g must:

Convert color attributes to an internal re pr esentation that can be poured through the page marking stencil onto the destination via some logical oper ation .

Convert multiple-bit-per-pixel color raster to an internal representation that c an be merge d into th e destinatio n via some logical operation.

Color processing must have access to the following state variables, which indic ate the for m and attribu tes by whic h the two color groups are g ener ated.

Halftone (rendering algorithm) RGB gamma correction Device-dep endent color lookup tables for eac h of the

three primaries

Chapter 2 describes in more detail how color raste r data is specified.

Color Printing Overview 1-13Color Printing Overview 1-13

U sing Color M odesU sing Color M odes

Introduction The PCL printer lang uag e has fou r color modes:

Black-and- Wh ite Simple Color PCL Imaging HP-GL/2 Imaging

PCL allows you to use any mode or combination of modes to accomplish your printing objective s most effic ien tly.

All four of the color modes create a palette. The palette for each mode is discussed in the section desc ribin g that mode, and also in Chapter 3 (“Using Palettes”).

Black-and-White

Mode (Default)

Black-and- Wh ite Mod e is the defau lt colo r mode. PCL devices power up in this mode and revert bac k to it whenever the printer receives an ?E reset. Black-and- Wh ite mo de i s also selectable using the Simple Color command (?*r1U). This mode creates an unmodifiable, default 2-pen palette, with white at index 0 and black at index 1 (compatible with ex isting mon ochr ome PCL 5 printer s).

Simple Color Mode Simple Color Mode, entered by the Simple Color command

(?*r#U), creates a fixed-size, fixed- color, unmodifiable palette. Dependin g on the value field, ?*r#U can create a 2-pen Black-and- Wh ite palette, an 8-pen RGB palette, or an 8-pen CMY palette. When using the Simple Color mode, the pixel encoding mode is always indexed planar.

PCL Imaging Mode PCL Imaging Mode, enabled by the Configure Image D a t a

command (?*v#W), allows a maximum of 24 bits per pixel for color specific ation . Theref ore, mor e color s (prod uc ed by halftoning) may be specifie d than are obtainable in Simple Color Mode. In the PCL Imagin g M ode, p ixe l en c oding mode, bits per pixel, bits per primary, white/black references, and the color palette are all programmable .

HP-GL/2 Imaging

Mode

In HP-GL/2, the Initialize (IN) command starts color imaging and perf or m s the following:

Sets the pixel encoding mode to ind ex by plane . Sets bits per index to 3. Creates an 8-pen palette that is reprogrammable in

either PCL or HP-G L/2 con tex t s (see Chapter 3, “Usin g Palettes,” for more information ).

Although default HP- GL /2 palettes are differen t than default PCL palettes, an HP-GL/ 2 palette is modifiable in either PCL or HP-G L/ 2 (u sin g the Assig n Color Index [?*v#I] or Pen Color [PC] commands, respectiv ely ). Likewise, a PCL palette created by the Con figure Imag e Data command (?*v#W) is modifiable in both PCL an d HP-GL/2 using the same comman ds.

The active palette is always transferred between HP-GL/2 and PCL contex ts. Sinc e only one palette at a time can be active, a new palette created in either contex t overwr ites the current palette.

2-2 Using Color Modes2-2 Using Color Modes

Simple Color Mode

The Simple Color command (?*r#U) spec ifies colo r selection from a fixed palette. RGB or CMY raster data must be sent by plane (?*b#V) as well as by row (?*b#W). The last plane in each row is sent using the ?*b#W command; all other planes are sen t using the ?*b#V command. In Simple Color mode, the pixel en c odin g mode is always indexed planar.

Simple Color

Command

The Simple Color command creates a fixed-size palette, whose color specification cannot be modified.

?*r#U # = –3 – 3 planes, device CMY palette

1 – Single plane K (Black) palette 3 – 3 planes, device RG B palette

Default = 1 Range = –3, 1, 3

The absolute value of the value field specif ies the number of planes per row of raster data to be sent. The number of entries in the new palette is 2

1. For example, a 3-plane palette has 8 entries, with index numbers 0 to 7.

This command destroys the activ e palette and creates a new palette, which beco mes the active palette . When the Simple Color mode is active, PCL and HP -G L/2 comman d s that modify the palette are locked out (NP, PC, ?*v#A, ?*v#B, ?*v#C, ?*v#I). When a Simple Color palette is popped from the stack ( ?*p#P), it cannot be modified, and the pixel encoding mode reverts to indexed planar.

A value field of 1 creates a 2-entry Black-and-White default palette.

, with index values 0 to 2n –

Usi ng Color Modes 2 -3Usi ng Color Modes 2 -3

A value field of 3 creates an 8-entry Device RGB palette (compatible with a PCL Imaging Mode palette, but not an HP-GL/2 default (IN) palette).

A value field of –3 creates an 8-entry palette in De vice CMY color space.

The Simple Color palettes are show n below :

Single Plane (value = 1)

Index Color

0 White 1 Black

3-Plane RGB (value = 3)

Index Color

0 Black 1 Red 2 Green 3 Yellow 4 Blue

2-4 Using Color Modes2-4 Using Color Modes

5Magenta 6 Cyan 7 White

3-Plane CMY (value = –3)

Index Color

0 White 1 Cyan 2Magenta 3 Blue 4 Yellow

Index Color

5 Green 6 Red 7 Black

PCL Im aging Mode

Configure Image

Data (CID)

Command

The PCL Imaging mode, entered using the Configure Image Data (CID) command (?*v#W), creates a variable-sized programmable palette. It provides half ton ing in the printer, with multiple color spaces, pix el en codin g mode s, and reprogrammable palettes.

The CID command provides con fig u ration infor mation for creating palettes and tran smitting raster data. The CID command performs the following:

Designates the color space for the defau lt palette Designates the size of the palette to be created Provides data for transf or ming color - sp ace -spec ific

values into device-specific values Provides data for transfor ming devic e-de penden t data

(monitor RGB) to device- ind epen de nt (Colorimetric RGB) Designates the format of ra ster data and how primary

components are combined to yie ld the r aste r representation

?*v#W[binar y da ta]

# = Number of data bytes

Default = NA Range = Short form: 6 bytes

Long form: >6 bytes

Usi ng Color Modes 2 -5Usi ng Color Modes 2 -5

Invalid config ur ation s of the CID comman d are igno re d and the data discarded. An y sign s in the value field are ignor ed.

The data fields in this command must contain byte-alig ned binary data, not ASCII data.

This command has two forms: the six-byte sho rt for m described below, and the long form consisting of these six bytes, plus additional in formation spe cif ic to the color space .

Common 6-Byte

Header

The short and long form s of the CID command use a common 6-byte header, regardless of which color space is specified. The header data fields, whose mean ing may v ary according to the color spaces, are present in all color space specification s. Th e short for m and lon g for m of the CID command are explained separ ately in the following pag es.

Byte 15 (MSB) 8 7 0 (LSB) Byte

Color space (UBYTE)

Bits/index (UBYTE)

Bits/primary # 2 (UBYTE)

Byte 0 (Color Space)

This byte specifies the color space. The range of values is 0 through 4. All oth er v alues are ignor ed.

Byte V alue Color Space

0 Device RGB (defaul t)

Pixel encoding mode (UBYTE)

Bits/primary # 1 (UBYTE)

Bits/primary # 3 (UBYTE)

2-6 Using Color Modes2-6 Using Color Modes

1 Device C M Y 2 Colorimetric RGB Spaces 3 CIE L*a*b* 4 Luminance-Chrominance Spaces

Note Colorimetric RGB color spaces are based on the 1931

standard 2-deg re e ob server and specified by CIE xy chromaticity coordinate s. They use the standard D6500 viewing illuminan t and a 45-deg r ee illumination model with a 0-degree co llec tor geometry for reflective data.

CIE L*a*b* is the CIE 1976 Uniform Color Space based on the 1931 standard 2-degre e observ er, and using a 45-degree illumination model with a 0-degree c ollec tor geometr y for reflective data. Th e viewin g illumin an t is the standard D6500 illuminant.

Luminance-Chromin an ce spaces are a 3x3 linear transformatio n from Color imetr ic RGB. Like CIE L*a*b*, achromatic data is contained in one channel an d chr omatic data shares the other two chan nels.

Byte 1 (Pixel Enco di n g Mo de)

Byte number 1 designates the format in whic h raster data is to be transmitted and interprete d. Th e range of this value field is 0 to 3. All other values for this field are ignored.

Byte V alue Pi xel En co ding Mod e Restrictions

Indexed by Plan e (default)

Bits/index must be 1, 2, 3, 4, 5, 6, 7, or 8

Indexed by Pixel Bits/index must be

1, 2, 4, or 8

Direct by Plan e 1 bit per primary

(RGB or CMY only)

Direct by Pixel 8 bits per primary

(All Color Spaces)

You need one plane or on e bit/ pixel for each power of two colors in the palette. For examp le, a 256-co lor palett e requires 8 plane s or 8 bits/pixel (2

= 256).

Usi ng Color Modes 2 -7Usi ng Color Modes 2 -7

MODE 0: INDEXED BY PLANE In mode 0 (default), succ essiv e plane s of data are sent for

each raster row. A plane contains one bit for each pix el in a row. A pixel is not fully def ine d until it has r eceiv ed all the planes for that row. The planes in a row form index numbers that define a pixel by se lec ting a palette entr y. Assuming 3 bits per index, the underlined column of bits below is the palette index for pixel 3 of row 1 (i1 is lsb; i3 is msb). Note that the T ran sf er Raster Data by Plane command (?*b#V) is used for all planes except the last plane of each row, which uses the Tr an sfer Raster Data by Row command (?*b#W).

Example:

?*b#V row 1 plane 1 i1 i1 ?*b#V plane 2 i2 i2 ?*b#W plane 3 i3 i3 ?*b#V row 2 plane 1 i1 i1 i1 i1 i1

?*v6W 00 00 03 08 08 08 # Binary data for CID

represented in hex. Sets color space to RGB, pixel encoding mode to 0, palette size to 8 (3 planes), last 3 bytes ignored.

?*r1A # Start raster . ?*b1V10110000 . . . # Transfer plane 1 (the first

bit for each pixel in the first row). Combining each bit with its corresponding bit in the other plane s forms the palette index number for that pixel.

?*b1V011 10000 . . . # T ran sfer plane 2 (the

second bit for each pixe l in the row).

i1 i1 i1 i2 i2 i2 i3 i3 i3

2-8 Using Color Modes2-8 Using Color Modes

?*b1W10101000 . . . # T ran sfer plane 3 (the third

bit for each pixel in the row) and move to the next row. Note that the ?*b#W command is used to send the last plane of each row.

Usi ng Color Modes 2 -9Usi ng Color Modes 2 -9

Example:

MODE 1: INDEXED BY PIXEL In mode 1, each pixel in a row i s fully specifie d befor e any

bits are sent for the next pixel. The bits for each pix el form a palette index number. Assuming 4 bits per index, the underlined block below is the palette index for pixel 2 of row 1 (i1 is lsb).

?*b#W row 1 i4 i3 i2 i1 ?*b#W row 2 i4 i3 i2 i1 i4 i3 i2 i1 . . . ?*b#W row 3 i4 i3 i2 i1 i4 i3 i2 i1 . . .

?*v6W 00 01 04 04 04 04 # Binar y data for CID

?*r1A # Start raster. ?*b1W45 # Most significant nibble

?*b1W6A # First pixel is index 6,

?*b1W03 # First pixel is index 0,

i4 i3 i2 i1 . . .

represented in hexidecimal. Sets color space to RGB, pixel encoding mode to 1, palette size to 16 (4 bits to address palette index). Last 3 bytes ignor ed.

selects palette index 4 for the first pixel. Second pixel is set to index 5. Move to the ne xt row.

second pixel is index 10. Move to the next row.

second pixel is index 3. Move to the next row.

2-10 Using Color Modes2-10 Using Color Modes

Example:

MODE 2: DIRECT BY PLANE In mode 2, the color raster data f or eac h row i s down loaded

by sequential planes, but the pixel c olor is direc tly specified, rather than forming an index into the palette. The underlined block below def ine s the actu al primar ies for pixel 3 of row 1.

?*b#V row 1 red plane r r ?*b#V green plane g g ?*b#W blue plane b b ?*b#V row 2 red plane r r r r r

?*v6W 00 02 01 01 01 01 # Binary data for CID

represented in hex. Sets color space to RGB, pix el encoding mode to 2. Palette size is ignored because this is a direct selection, not indexed. Last 3 bytes are always 1 for this mode.

?*r1A # Start raster. ?*b1V10110000 . . . # Transfer plane for primary

color 1. Each bit tu r ns on or off the red primary for the pixel defined by the corresponding bits in each plane.

?*b1V011 10000 . . . # T r ansfe r plane for primary

color 2. Each bit tu r ns on or off the green primary of the pixel.

?*b1W10101000 . . . # Transfer plane for primary

color 3 and move to the next row. Each bit turns on or off the blue primary of the pixel.

r rr g gg b bb

Using Color Modes 2-11Using Color Modes 2-11

Example:

MODE 3: DIRECT BY PIXE L In mode 3, the color raster data is down loaded pixel by pixel

(as in mode 1), but each pixel dire ctly specifies each color component (as in mode 2). Assumin g Device RG B spac e with 8 bits per primary, the underline d block below defin e s the actual color primar ies for pix el 1 of row 2.

?*b#W row 1 r7–r0 g7–g0 b7–b0 . . . ?*b#W row 2

r7–r0 g7–g0 b7–b0 . . .

?*b#W row 3 r7–r0 g7–g0 b7–b0 . . .

?*v6W 00 03 00 08 08 08 # Binary data for CID

represented in hex. Sets color space to RGB, pixel encoding mode to 3. Palette size is ignored. Send 8 bits to address each primary valu e for a pixel.

?*r1A # Start raster. ?*b3W 45 06 30 # Each byte sets a primary

value for the first pixel and moves to the next row (45 specifies the red, 06 the green, and 30 the blue component value of that pixel).

2-12 Using Color Modes2-12 Using Color Modes

Byte 2 (Number of Bits per Index)

In all pixel encodin g modes, this byte sets the size of the palette to 2

, where n is the number of bits per index.

In pixel encodin g modes 0 and 1 (index ed ), whe re raster data is interpreted as indices into a palette, this value specifies the number of bits required to acce ss all palette entries.

In pixel encoding modes 2 and 3 (direct), this value determines palette size, but has no effect on the specification of raster data.

Byte 3 (Number of Bits for Primar y #1 )

This byte is ignored in pixel enc od ing modes 0 and 1, but affects the black and white re fer en ces in device -dep en den t color spaces. In Devic e RG B, the black refer en c e for primary #1 is set to 0 and the white referenc e is set to

– 1, where n is the number of bits for primary #1. These

referenc es are rev er sed in Devic e CM Y color space.

In pixel encoding mode 2, this byte is ignored except in Device RGB and Device CMY color space, where it designates the number of data bits needed to specify primary #1, as well as the number of data planes to be sent for primary #1.

In pixel encoding mode 3, this byte designates the number of data bits needed to specify primar y #1.

A value of 0 defaults the black and white ref er ence value s for primary #1 ac c or ding to the color space.

Byte 4 (Number of Bits for Primar y #2 )

This byte is ignored in pixel enc od ing modes 0 and 1, but affects the black and white re fer en ces in device -dep en den t color spaces. In Devic e RG B, the black refer en c e for primary #2 is set to 0, and the white reference is set to

– 1, where n is the number of bits for primary #2. These

referenc es are rev er sed in Devic e CM Y color space.

In pixel encoding mode 2, this byte is ignored except in Device RGB and Devic e CMY color spaces, wh ere i t designates the number of data bits needed to specify primary #2, as well as the number of data planes to be sent for primary #2.

In pixel encoding mode 3, this byte designates the number of data bits needed to specify primar y #2.

A value of 0 defaults the black and white ref er ence value s for primary #2 ac c or ding to the color space.

Using Color Modes 2-13Using Color Modes 2-13

Byte 5 (Number of Bits for Primar y #3 )

This byte is ignored in pixel enc od ing modes 0 and 1, but affects the black and white re fer en ces in device -dep en den t color spaces. In Devic e RG B, the black refer en c e for primary #3 is set to 0, and the white reference is set 2

– 1, where n is the number of bits for primary #3. These referenc es are rev er sed in Devic e CM Y space.

In pixel encoding mode 2, this byte is ignored except in Device RGB and Device CMY color space, where it designates the number of data bits needed to specify primary #3, as well as the number of data planes to be sent for primary #3.

In pixel encoding mode 3, this byte designates the number of data bits needed to specify primar y #3.

A value of 0 defaults the black and white ref er ence value s for primary #3 ac c or ding to the color space.

2-14 Using Color Modes2-14 Using Color Modes

Short Form of

CID Command

(Configure

Image Data)

The Short Form of the CID command involve s sendin g just the common 6-byte header. By changing the value of byte 0 (color space ), the short form c an spec ify the follow ing fiv e color spaces:

Device RGB ?*v6W[0x00, . . . ] Device CMY ?*v6W[0x01, . . . ] CIE L*a*b* ?*v6W[0x 03, . . . ]

The following data rang es are allowed in CIE L*a*b*. Hue is preserved when out-of -r ang e data is clipped.

L* = 0.0 to 100.0 a* = –100.0 to 100.0 b* = –100.0 to 100.0

Colorimetric RGB (SMPTE RGB) ?*v6W[0x02, . . . ]

Non-linear SMPTE RGB with a 2.2 gamma and 1.0 gain is the default Color imetr ic RGB color space . The shor t for m allows the following ranges:

R = 0.0 to 1.0 G = 0.0 to 1.0 B = 0.0 to 1.0

Luminance-Chrominance (YUV) ?*v6W[0x04, . . . ]

YUV, which is a linear tran sformation from SMPTE RGB, is the default Luminanc e-Ch romin an ce color sp ace . The short form allow s the follow in g rang es:

Y = 0.0 to 1.0 U = –0.89 to 0.89 V = –0.70 to 0.70

Using Color Modes 2-15Using Color Modes 2-15

Data Range Sca ling

White and black refer en ces defin e the encodin g range for devic e-de pen den t co lor spaces. Ho we ve r, deviceindependen t color spaces requ ire input data pre- scaled to the range 0 to 255. For examp le, to use th e short for m for the default YUV color space , th e input data mu st hav e th e following ranges:

Y = 0.0 to 1.0 U = –0.89 to 0.89 V = –0.70 to 0.70 The user must linearly scale (y = mx + b) the input data to

the range 0 – 255: Y = 0 (0.0) to 255 (1.0) U = 0 (–0.89) to 255 (0.89) V = 0 (–0.70) to 255 (0.70)

2-16 Using Color Modes2-16 Using Color Modes

Long Form of

CID Command

(Configure

Image Data)

Note The short form for the De vic e RGB color space defau l ts

In addition to the short form, th er e is also a long form of the CID command for eac h color space. In devic e-in de pen den t color spaces, the lon g form can spec ify primar ies othe r than the defaults provided by the short form. For example, a Sony T r initron RGB primary base can be selecte d for Colorimetric RGB instead of the default no n- line ar SMPTE RGB primaries.

Device RGB (Long Form)

The long form for the D evice RGB colo r spac e (valu e field

18) provides explicit entr y of black and white ref er ence s (range is –32767 to 32767). Black and white refer ence s are used in the direct pix el encod ing modes (2,3) to set relative limits for raster data; they are also used when specifyin g the primary components of new palette entries (?*v#A, ?*v#B, ?*v#C). Black and white referenc es hav e no effec t on CID default palette colors. Th e refer enc e values are specified as 16-bit signed integers (sint16).

each primary’s black refere nce to 0 and the white ref eren ce

to 2

–1, where n is the number of bits for that primary.

Byte 15 (msb) 8 7 (lsb) 0 Byte

0 Colo r space Pixel encoding mode 1 2 Bits per index Bits per primary #1 3 4 Bits per primary #2 Bits per primary #3 5 6 White r efer en ce for primar y #1 (sint 16) 7 8 White r efer en ce for primar y #2 (sint 16) 9 10 White reference for primary #3 (sint 16) 11 12 Black reference for primary #1 (sint16) 13 14 Black reference for primary #2 (sint16) 15 16 Black reference for primary #3 (sint16) 17

Using Color Modes 2-17Using Color Modes 2-17

Device CMY (Long Form)

The long form for the D evice CMY color sp ace (value field i s

18) provides explicit entr y of black and white ref er ence s (range is –32767 to 32767). Black and white refer ence s are used in the direct pix el encod ing modes (2,3) to set relative limits for raster data; they are also used when specifyin g the primary components of new palette entries (?*v#A, ?*v#B, ?*v#C). Black and white referenc es hav e no effec t on the default CID palette color s. The refere nce value s are specified as 16-bit signed integers (sint16).

Note The short form for the Device CM Y color space def aults

each primary’s white refer en ce to 0 and black r efer enc e to

–1, where n is the number of bits for that primary.

Byte 15 (msb) 8 7 (lsb) 0 Byte

0 Color space Pixel encodin g mode 1 2 Bits per index Bits per primary #1 3 4 Bits per primary #2 Bits per primary #3 5 6 White reference for primary #1 (sint16) 7

8 White reference for primary #2 (sint16) 9 10 White referen ce for primary #3 (sint16) 1 1 12 Black referenc e for primary #1 (sint16) 13 14 Black referenc e for primary #2 (sint16) 15 16 Black referenc e for primary #3 (sint16) 17

2-18 Using Color Modes2-18 Using Color Modes

CIE L*a*b* (Long Form)

The long form for the CIE L*a*b* color space allows a larger data range than the shor t form defaults:

L* = 0.0 to 120.0 (greater than the short form by 20.0) a* = –159.0 to 128.0 (less than the short form by –32.0 and

greater than the short form by 28.0) b* = –120.0 to 80.0 (less than the short form by 20.0)

Note Although the data ranges may ex ten d bey ond the def ault

data ranges specified in the shor t for m of the CID command, the printer will c lip the data to the short form data ranges.

Maximum and minimu m valu es are spec ified for eac h primary color. Floating point data must be linearly scaled (y = mx + b) to the range 0 – 255.

Since a* and b* have no theor etic al limits, L*a*b* data may be sent outside CID constraints. Then data is clipped to preserve hue and compressed to the device’s printable gamut.

Using Color Modes 2-19Using Color Modes 2-19

The white point is based on the standard D6500 illumin ant.

Byte 15 (msb) 8 7 (lsb) 0 Byte

0 Color space Pixel encoding mode 1 2 Bits per index Bits per primary # 1 3 4 Bits per primary #2 Bits per primary #3 5 6 Minimum L* value (most significan t wor d) * 7

8 Minimum L* value (least significan t wor d) * 9 10 Maximum L* value (msw) 11 12 Maximum L* value (lsw) 13 14 Minimum a* value (msw ) 15 16 Minimum a* value (lsw ) 17 18 Maximum a* value (msw ) 19 20 Maximum a* value (lsw ) 21 22 Minimum b* value (msw ) 23 24 Minimum b* value (lsw ) 25 26 Maximum b* value (msw ) 27 28 Maximum b* value (lsw ) 29

FLOATING PO INT FO RMA T* The following format is used for device -in dependent color

floating point specifications:

2-20 Using Color Modes2-20 Using Color Modes

31 30 23 22 0

Sign Exponent Fractional Portion

The above single-prec ision , 32-bit floatin g point specification is fully complian t with the IEEE Floating Point Formats.

Colorimetric RGB (Long Form)

The long form for Colorimetric RGB allows specificatio ns other than the def ault n on -lin ear SMPTE RGB with a 2.2 gamma and 1.0 gain. Each RGB primar y and th e white point is specified in the CID data field by chr omatic ity coordinates (CIE xy). Th e tristimulu s lumin anc e Y value of the white point is assumed to be 100% and is therefo re not specified. For color spaces that are lin ear tran sfor mation s from CIE XYZ tristimulus coord inate s, gamma and gain are set to 1.0; otherwise they are set appro priately. Colorime tric RGB spaces can be used for any monitor having primaries specified as CIE xy chromaticity coordinates with white point, such a s the Son y Trinitron or Hitachi Color Monitor.

Byte 15 (msb) 8 7 (lsb) 0 Byte

0 Color space Pixel encoding mode 1 2 Bits per Index Bits per primary #1 3 4 Bits per primary #2 Bits per primar y #3 5 6 x Chromaticity for red primary (msw) 7 8 x Chromaticity for red primary (lsw) 9 10 y Chromaticity for red primar y (msw) 11 12 y Chromaticity for red primar y (lsw) 13 14 x Chromaticity for gr een pr imary (msw) 15 16 x Chromaticity for gr een pr imary (lsw) 17 18 y Chromaticity for gr een pr imary (msw) 19 20 y Chromaticity for gr een pr imary (lsw) 21 22 x Chromaticity for blue primar y (msw) 23 24 x Chromaticity for blue primar y (lsw) 25 26 y Chromaticity for blue primar y (msw) 27 28 y Chromaticity for blue primar y (lsw) 29 30 x Chromaticity for white poin t (m sw) 31 32 x Chromaticity for white poin t (l sw) 33 34 y Chromaticity for white poin t (m sw) 35 36 y Chromaticity for white poin t (l sw) 37

Using Color Modes 2-21Using Color Modes 2-21

38 Gamma for red primary (msw) 39 40 Gamma for red primary (lsw) 41 42 Gain for red primary (msw) 43 44 Gain for red primary (lsw) 45 46 Gamma for green primary (msw) 47 48 Gamma for green primary (lsw) 49 50 Gain for green primary (msw) 51 52 Gain for green primary (lsw) 53 54 Gamma for blue primary (msw) 55 56 Gamma for blue primary (lsw) 57 58 Gain for blue primary (msw) 59 60 Gain for blue primary (lsw) 61 62 Minimum re d value (msw) 63 64 Minimum red value (lsw) 65 66 Maximum re d value (msw) 67 68 Maximum red value (lsw) 69 70 Mi nimum green value (msw) 71 72 Minimum green value (lsw) 73 74 Ma ximum green value (msw) 75 76 Maximum green value (lsw) 77 78 Minimum blue value (msw) 79 80 Minimum blue value (lsw) 81 82 Maximum blue value (msw) 83 84 Maximum blue value (lsw) 85

2-22 Using Color Modes2-22 Using Color Modes

Luminance-Chrominance (Long Form)

The long form for Lumin an c e-Ch r omin anc e allow s color spaces other than th e default Y U V, such as Kodak Photo YCC, the proposed JPEG and TIFF 6.0 YCrCb standard, YES, and YIQ. These Luminance-Chrominance color spaces are derived fro m the Color imetr ic RGB space u sing a 3x3 transformation matrix. The tristimulus luminance y value of the white point is assumed to be 100% and is therefore not specified.

Byte 15 (msb) 8 7 (lsb) 0 Byte

0 Color space Pixel encoding mo de 1

2 Bits per index Bits per primary #1 3

4 Bits per primary #2 Bits per primar y #3 5

6 Encoding for pr imary #1 R (msw) 7

8 Encoding for pr imary #1 R (lsw) 9

10 Encoding for pr imary #1 G (msw) 11

12 Encoding for pr imary #1 G (lsw) 13

14 Encoding for primary #1 B (msw) 15

16 Encoding for primary #1 B (lsw) 17

18 Encoding for primary #2 R (msw) 19

20 Encoding for primary #2 R (lsw) 21

22 Encoding for pr imary #2 G (msw) 23

24 Encoding for pr imary #2 G (lsw) 25

26 Encoding for primary #2 B (msw) 27

28 Encoding for primary #2 B (lsw) 29

30 Encoding for primary #3 R (msw) 31

32 Encoding for primary #3 R (lsw) 33

34 Encoding for pr imary #3G (msw) 35

36 Encoding for pr imary #3 G (lsw) 37

38 Encoding for primary #3 B (msw) 39

40 Encoding for primary #3 B (lsw) 41

42 Minimum primary #1 valu e (m sw) 43

44 Minimum primary #1 valu e (l sw) 45

46 Maximum primary #1 valu e (m sw) 47

48 Maximum primary #1 valu e (l sw) 49

Using Color Modes 2-23Using Color Modes 2-23

50 Minimum primary #2 valu e (m sw) 51 52 Minimum primary #2 valu e (l sw) 53 54 Maximum primary #2 valu e (m sw) 55 56 Maximum primary #2 valu e (l sw) 57 58 Minimum primary #3 valu e (m sw) 59 60 Minimum primary #3 valu e (l sw) 61 62 Maximum primary #3 valu e (m sw) 63 64 Maximum primary #3 valu e (l sw) 65 66 x Chromaticity for red primary (msw) 67 68 x Chromaticity for red primary (lsw) 69 70 y Chromaticity for red primary (msw) 71 72 y Chromaticity for red primary (lsw) 73 74 x Chromaticity for gree n primar y (msw) 75 76 x Chromaticity for gree n primar y (lsw) 77 78 y Chromaticity for gree n primar y (msw) 79 80 y Chromaticity for gree n primar y (lsw) 81 82 x Chromaticity for blue primary (msw) 83 84 x Chromaticity for blue primary (lsw) 85 86 y Chromaticity for blue primary (msw) 87 88 y Chromaticity for blue primary (lsw) 89 90 x Chromaticity for white poin t (msw) 91 92 x Chromaticity for white poin t (lsw) 93 94 y Chromaticity for white poin t (msw) 95 96 y Chromaticity for white poin t (lsw) 97 98 Gamma for red primary (msw) 99 100 Gamma for red primary (lsw) 101 102 Gain for red primar y (m sw) 1 03 104 Gain for red primar y (l sw) 105 106 Gamma for green primary (msw) 107 108 Gamma for green primary (lsw) 109 11 0 Gain for green primary (msw) 11 1 11 2 Gain for green primary (lsw) 11 3 114 Gamma for blue primary (msw) 115 116 Gamma for blue primary (lsw) 117 11 8 Gain for blue primary (msw) 119

2-24 Using Color Modes2-24 Using Color Modes

120 Gain for blue primary (lsw) 121

Examples Using

the CID Command

Example: The short form CID command, as a C function, can look

The following examples illustrate u sing the CID command’s short and long forms for each color sp ace . For clarity, data is shown as ASCII, rath er than binary and the CID command (?*v#W) is shown as “CID”. Th e follow in g for ma t is used:

CID ( data , data , . . . )

Device RGB or Device CMY

SHORT FORM CID(0,1,8, 8,8, 8) Device RGB, 8 bits/pixel indexed CID(1,1,8, 8,8, 8) Device CMY, 8 bits/pixel indexed

like this:

short_cid(Co lor _mode , Pixel_mod e, Bitsper Index , BitsperColor_1, Bitspe rCo lor _2, Bitsper Color _3) { int Color_mode, Pixel_mode , BitsperIndex, BitsperColor_1, Bitspe rCo lor _2, Bitsper Color _3;

printf(“\033*v6W%c%c%c%c%c%c”,Color_mode, Pixel_mode, BitsperIndex, BitsperColor_1, BitsperColor_2, BitsperColor_3); }

LONG FORM

CID(0,1,8, 8,8, 8, Device RGB, 8 bits/pixel indexed 0,0,0 White reference 100,100,100) Black reference

Using Color Modes 2-25Using Color Modes 2-25

CIE L*a*b*

SHORT FORM CID(3,3,0, 8,8, 8) L*a*b*, direct 8 bits/primary

LONG FORM CID(3,3,0, 8,8, 8, L*a*b*, direct 8 bits/primary

0.0, 100.0, L* data encoding –100.0, 100.0, a* data encoding –100.0, 100.0) b* data encoding

Non-Linear SMPTE RGB, 2.2 Gamma, 1.0 Gain

SHORT FORM CID(2,3,0, 8,8, 8) RGB, direct 8 bits/primar y

LONG FORM

CID(2,3,0,8,8,8,

0.64, 0.34,

0.31, 0.60,

0.16, 0.07,

0.3127, 0.3290,

2.2, 1.0,

0.0, 1.0,

0.0, 1.0)

2-26 Using Color Modes2-26 Using Color Modes

Non-Li nea r Son y Trinitron

SHORT FORM Not Applicable LONG FORM CID(2,3,0,8,8,8

0.62, 0.34,

0.30, 0.58,

0.15, 0.09,

0.2800, 0.2933,

2.3, 1.19,

0.0, 255.0,

0.0, 255.0)

YUV Chrominance-Luminance Color Space

SHORT FORM CID(4,3,0, 8,8, 8) YUV, direct 8 bits/primary

YUV Chromi nance -Lumi n ance wit h So ny Trinitron

LONG FORM

CID(2,3,0,8,8,8

0.30,0.59,0.11, –0.30,0.59,0.89,

0.70,–0.59,–0.11,

0.0,255.0 –227.0,227.0, –179.0,179.0

0.62,0.34,

0.30,0.58,

0.15,0.09,

0.2800, 0.2933,

2.3,1.19,

2.3,1.19)

Using Color Modes 2-27Using Color Modes 2-27

HP-GL/2 Imaging Mode

The HP-GL/2 Imaging Mode pr ovides a way of using vector commands in printing docu men ts. Although the default PCL and HP-GL/2 palettes are not the same, when transferrin g from PCL to HP-G L/2, ac tive palet te information does stay th e same. You can switch betw een PCL and HP-GL/ 2 and use th e same palette, and you can also modify palettes using either PCL or HP-GL/2.

Compared to monochrome printers, the Color LaserJet and DeskJet 1200C color printers have some commands tha t are new and/or modified for use with colo r pr in ters. Chapter 7 describes the new or modified HP-G L/ 2 commands.

If you are not familiar with usin g HP-GL/ 2, se e the PCL 5 Printer Language Technica l Reference Manu al. It provides a detailed explanation of using HP-GL/2.

2-28 Using Color Modes2-28 Using Color Modes

U sing PalettesU sing Palettes

Introduction A palette is a collection of color specifications selected using

index numbers. Th e figur e below illustr ates a palette. Each palette entry associates an index numbe r with th ree primary color comp onen t s. For HP-GL/ 2 purposes on ly, a pen width is also associated with each palette entry.

In non-raster mode, the current palette contains all the colors available to the printer. In raster mode, indexed color selection uses the palette, but direc t selectio n does not.

Default palettes are created by all the PCL color mode s (Black and White, Simple Color, PCL Imaging, and HP-GL/2 Imagin g) . The activ e palette may be modified when in the PCL Imagin g or HP-G L/2 imag ing modes, but not when in the Simple Color or Black and White modes. When switching between PCL 5 and HP-GL/2 contexts, the active palette is automatically transferred.

Multiple palettes can exist in th e system via the Palette ID and Palette Stack mechanism. However, only one palette at a time can be active. A palette created in the PCL co nte xt remains active and unchanged when switching to the HP-GL/2 con tex t, and a palette created in th e HP-G L/ 2 context remains active and unchanged when switching to the PCL contex t. Per fo rmin g a reset or ente rin g PJL overwrites th e activ e palette with th e defau lt black and white palette.

Whenever a new palette is created, th e curre ntly or previously ac tiv e palette is destr oyed. A new palette is created by power -on and also by the following commands:

PCL Reset (?E) Simple Color (?*r#U) Configure Image Data (?*v#W) HP-GL/2 Initialize (IN)

The active palette can be saved by pushin g it onto the palette stack with the Push/Po p Palette command (?*p#P). Popping a palette from the stack destro ys the active palette—the popped palette bec omes the active palette.

3-2 Using Palettes3-2 Using Palettes

Saving the Palette The curren t palette is destroyed when a new palette is cre-

ated. The Push/Pop Palette command (?*p#P) can save (push) the curr ent palette and then restore (po p) it.

Push/Pop Palette

Command

This command pushes or pops the palette from the palette stack.

?*p#P

# = 0 Push (save) palette

1 Pop (restore) palette

Default = 0 Range = 0, 1 (invalid v alues are ignored)

A value of 0 (?*p0P) pushes a copy of the active palette onto the palette stack. When a palette is pushed, the active palette is not affected.

A value of 1 (?*p1P) pops the most recently pushed palette and destroys the activ e palette; the popped palette bec omes the active palette. As with any stack, the last item pushed is the first item popped.

Pushing a palette saves the following parameters:

Color definition s for eac h palette en try Pen widths (for HP-GL/2 use) Color space specification Black and white refer en ces Number of bits per index Pixel encodin g mode Number of bits per primary Gamma correction View in g illuminan t Color lookup tables

Usi ng P alettes 3-3Usi ng P alettes 3-3

Render algo rithm Downloaded dith er matrix

Pushing a palette does not save the follow in g parameter s.

Foreground color Color components: 1st, 2nd, and 3rd Finish mode Monochrome print mode

The palette stack depth is limited by printer memory. Attempts to push a palette with insufficient memory cause an out-of-memor y err or. Attempts to pop from an empty stack are ignored.

Macros can push and po p palettes. A palette that wa s popped in an executed macro remains in effect at the end of the macro (thi s is not true for “called” or “over laid” macr os).

PCL reset commands (?E) and exits to PJL cause the printer to empty the palette stack an d overw rite the activ e palette with a non-programmable black an d white palette. The HP-GL/2 command s IN and DF have no effect on the palette stack, but they do destroy the active palette and replace it with the default HP- GL/2 palette.

3-4 Using Palettes3-4 Using Palettes

Palette Management by ID

All palettes hav e a unique ID (identification number). The default black and white palette create d on power -u p or ?E has an ID of 0.

Palette management by ID lets applications have multiple palettes. As shown below, multiple palettes can exist in two areas: the palette stack and the palette store. The stack holds palettes that are pushed via a Push /P op Palette co mmand; the store holds palettes havin g palette IDs.

Usi ng P alettes 3-5Usi ng P alettes 3-5

Palettes on the stack may not be selected by ID, since only a copy of a palette is pushed onto the stack; the original palette and ID remain in the palette stor e. A palette popped from the stack goes into the pale tte store, beco mes the ne w active palette, an d assumes the ID of the pr eviou sly activ e palette, which is overwritten. Only one palette at a time may be active.

Management by ID allows applications to tag d ata, hav e multiple raster conf igur ation s, and have palettes for different color spaces—all withou t re conf igu rin g the activ e pa lette. For example, one palette can be created for PCL text, one for HP-GL/2 primitives, one for simple raster, and one for 24-bit raster. The applicatio n can then switch between palettes according to what is being sent to the prin ter.

Selecting a new active palette changes the PCL grap hic s state. Besides color entries, a palette also contain s the graphics state at the time the bitmap represen tation of the palette colors was created . This guaran tees co lor reprod uc tion integrity by insuring that the same color specification triplet always produ ces th e same bitmap represen tation .

As described below, the Select Palette (?&p#S), Palette Con- trol (?&p#C), and Palette Contr ol ID ( ?&p#I) commands implement the three basic operatio ns of manageme nt by ID.

Selection of the active palette Deletion of palettes Copying of palettes

3-6 Using Palettes3-6 Using Palettes

Select Palette

Command

The Select Palette comman d selects a new active palette by specifyin g an ID number. The previously active palette i s unchanged.

?&p#S

# = Palette ID number

Default = 0 Range = 0 to 32767 (command is ignored for out-

of-range values)

This command activates the designated palette in the palette store. The command is ignored if the specifie d ID matches the active palette’s ID, or if no palette with that ID exists. The designated ID is saved as the palette select ID in the curren t modified pr in t env ir onmen t.

This command can be used to de-select th e activ e palette and select as the new active palette a palette created by the Palette Control command (?&p#C). For example, to copy the active palette to an ID of 44 and select the new palette to use or modify, send ?&p44i6c44S.

When a palette creation command is receiv ed such as Configure Image Data (?*v#W), Simple Color (?*r#U), or an HP-GL/2 IN, the cre ated palette ov erw rite s the activ e palette and is assigned the curren t palette selec t ID, which is unchanged.

A palette popped from the stac k overw rite s the active palette, and is assigned the current palette select ID , which is unchanged.

?E resets the palette select ID value to 0 and deletes all palettes in the palette stack and palette store, includin g the active palette which is replaced by a default PCL fixed black and white palette with a palette selec t ID valu e of 0.

Usi ng P alettes 3-7Usi ng P alettes 3-7

Macros affect the palette select ID valu e as follows:

Calling or Overlaying a macr o—sav es the ID valu e and a copy of the active palette. Upon macro exit, th e restor ed palette again becomes the active palette with the restored ID. An ex isting palette with this ID i s deleted.

Executing a macro —do es not save th e ID value or the active palette; changes re main in effect.

Palette Control ID The Palette Control ID command specif ies the ID number

to be used by the Palette Control Command .

?&p#I

# = Palette ID number

Default = 0 Range = 0 to 32767 (command is ignored for out-

of-range values)

3-8 Using Palettes3-8 Using Palettes

The ID number specifie d by this command is saved as the palette control ID in the curren t modifie d print environme nt and is used by the Palette Control co mmand (?&p#C).

?E or power-up resets the palette contr ol ID to 0, which is then the default black and white palette ID.

Macros affect the palette con tr ol ID value as follows:

Calling a macro—saves the value and r estor es the value at exit.

Executing a macro —do es not save th e value; chang e s remain in effect at exit.

Overlayin g a macro— copies the valu e befor e rese tting to 0, and restores at exit.

Palette Control The Palette Control command pr ovides a mech an i sm for

marking and deletion of palettes.

?&p#C # = 0 - Delete all palettes except tho se in the

stack (active palette delete d)

1 - Delete all palettes in the stack (active

palette is not affected)

2 - Delete palette (specified by Palette

Control ID )

6 - Copy active palette to ID specified by

Palette Control ID

Default = 0 Range = 0, 1, 2, 6 (command is ignored for

unsupported values)

A v alue of 0 deletes all palettes exce pt those on the palette stack. The active palette is replaced by the default black and white palette (ID 0). The palette control ID is not used.

A v alue of 1 clears the palette stack. The active pale tte is unaffected, an d the palette contr ol I D is not used.

A v alue of 2 deletes th e palette with th e specif ied palette control ID if it exists; other wise th e command is ign or ed. For example, to delete palette 53, send ?&p53i2C. If the active palette’s ID is specified the active palette i s replaced by the default blac k and white palette. This option does not chan ge the palette contr ol ID value .

Note When the active palette is replac ed by the defau lt black

and white palette, the graphic s state associate d with the previous palette is also replaced.

Usi ng P alettes 3-9Usi ng P alettes 3-9

A value of 6 creates a copy of the active palette. The copy receives the ID specif ied by th e last Palette Contr ol ID command. For example, to copy the active palette to a palette with an ID of 14, send ?&p14i6C. The copied palette overwrites any palette that alr eady has an ID equal to the palette control ID. The copie d palette does not become the activ e palette. The comman d is ignored if a palette is to be copied to its own ID.

The Palette Control command pr ov ides a way of manag ing system memory by deleting palettes in either the stack or store that are no longer in use.

Palette Control that is exerc ised durin g mac ros can have significan t impact on palettes that ex i st within the syste m. Deleting all palettes, or those on the stack, or the current palette, or all those except on the stack can have adver se effects when the macr o is exited. The adver se effe ct cou ld be the deletion of the desired palette, and replaceme nt with a black and white non-programmable palette.

3-10 Using Palettes3-10 Using Palettes

Simple Color Palettes

The Simple Color command (?*r#U) prov ides a quick way to select colors from a fixed, non-progr ammable palette.

The Simple Color command overwrites the curren t palette with one of the fixed pale ttes below. When the Simple Color command is in effect, the PCL and HP-G L/2 comman ds that modify a palette entry (NP, CR, PC, ?*v#A, ?*v#B, ?*v#C, ?*v*I, ?*t*I) are locked out. A popp ed simple c olor pale tte cannot be modified and th e pixe l enc odin g mode re ve rts to “index by plan e”. O nly the IN or the CID ( ?*v#W) commands can create a modifiable palette.

As shown below, a value field of 1 (?*r1U) creates a black and white palette. A valu e of 3 create s an 8-pen palette in Device RGB color space . A value of –3 create s an 8-pen palette in Device CMY co lor space. All of the se Simple Co lor palettes are fixed and non-progr ammable.

Single Plane (value = 1)

Index Color

0 White 1 Black

3-Plane RGB (value = 3)

Index Color

0 Black 1 Red 2 Green 3 Yellow 4 Blue 5Magenta 6 Cyan 7 White

Using Palettes 3-11Using Palettes 3-11

3-Plane CMY (value = –3)

Index Color

0 White 1 Cyan 2Magenta 3 Blue 4 Yellow 5 Green 6 Red 7 Black

3-12 Using Palettes3-12 Using Palettes

CID Color Pale ttes The Config ure Imag e Data comman d, explain ed in detail in

Chapter 2, creates a palette based upon the parameters in its data field. CID-created palettes are programmable: any entry can be re a ssig n ed a differ en t col o r usin g PC L commands (?*v#A, ?*v#B, ?*v#C, ?*v*I) or HP-GL/2 com- mands (CR, PC, NP). Default palettes vary by color space.

Device RGB

Palettes

The black and white refe renc es spec ified by the CID command have no effect on the defau lt palettes below. However, when a CID palette entry is reprogrammed with a different color, the black and white referen c es are used to specify the primar y compon ents of the n ew color.

Bits/I ndex = 1

Index Color

0 White 1 Black

Bits/I ndex = 2

Index Color

0 Black 1 Red 2 Green 3 White

Bits/Index = 3 through 8

Index Color

0 Black 1 Red 2 Green 3 Yellow 4 Blue 5Magenta

Using Palettes 3-13Using Palettes 3-13

6Cyan 7 White

n > 7 Black

Device CMY

and Device-

Independent

Palettes

A CID command spec ify in g eith er a devic e-in dependen t color space or the Device CMY color space creates the same default palettes. This is becau se devic e- ind epen de nt color s are transfor med in to the printer’s native space, Devic e CMY.

Bits/I ndex = 1

Index Color

0 White 1 Black

Bits/I ndex = 2

Index Color

0 White 1Cyan 2Magenta 3 Black

Bits/Index = 3 through 8

Index Color

0 White 1Cyan 2Magenta 3 Blue 4 Yellow 5 Green 6 Red 7 Black

n > 7 Black

3-14 Using Palettes3-14 Using Palettes

HP-GL/2 Palettes Regardless of the color space, a default PCL palette i s

always different th an a defau lt HP-GL/ 2 palette. The following table shows the default palettes established in HP-GL/2. Like a defau lt CID palette , a default HP-G L/ 2 palette can be modified in either PCL or HP-GL/2 conte xts using the following commands:

PCL

Color Components 1, 2, and 3 (?*v#A, ?*v#B, ?*v#C) Assign Color Index (?*v#I)

HP-GL/2

Number of Pens (NP) Pen Color A s sig n men t (PC) Set Relative Color Range (CR)

Note The IN command always establishes the 8-pen palette.

T wo Pens

Pen Number Color

0 White 1 Black

Four Pens

Pen Number Color

0 White 1 Black 2 Red 3 Green

Using Palettes 3-15Using Palettes 3-15

Eight Pens

Pen Number Color

0 White 1 Black 2 Red 3 Green 4 Yellow 5 Blue 6Magenta 7Cyan

n > 7 Black

3-16 Using Palettes3-16 Using Palettes

Foreground C olor All PCL marking entitie s utilize “foreg ro und” color, which is

selected from the curren t palette u sing the Foregr ou nd Color command (?*v#S). Foreground color interacts with raster color depen din g on the print model c omman ds in effect.

Foreground Color

Command

The Foreground Color comman d sets the fore grou nd co lor to the specified inde x of the curre nt palette.

?*v#S

# = Index number into curr en t palette

Default = 0 Range = 0 to 2

Specified values that are out-of -rang e of the curre nt palette are mapped into a new index as follows:

Index = Specified foreground index modulo palette size For example, spec ifying a foreg r ound color ind ex of 10 wh en

the current palette size is 8 maps to 10 modulo 8, which is equal to 2. If the current palette was created under HP-GL/2, the in dex is mapped acc or din g to the HP-G L/ 2 mapping function.

Foregroun d colo r affects the follow ing PCL page markin g primitives:

Text charac ter s (the y chan g e to the foreg rou n d colo r, including underlining)

Solid or monochrome pattern ed rectan g ular ar ea fills (rules)

Monochrome patterns (except HP-GL/2) Raster images

(current palette size)

– 1

Using Palettes 3-17Using Palettes 3-17

The following are no t affected:

User-def ine d color pattern s (for mat 1 down load patter ns) HP-GL/2 markin g primitives (HP- GL /2 uses “ selec ted

pen”, but ignor es for eg r ou nd color)

Note Foregroun d colo r inter acts with color raster images. In the

printer, all color raster is resolved into three binar y raste r planes of CMY. Foreground color is applied to these plane s, modifying the color image. For no interac tion , set foregroun d color to black wh en sendin g color ra ster images.

After a foreground co lor is selected, chan g in g any of the following will not chang e for egr oun d colo r until a new Foreground Color command (?*v#S) is issued:

Active Palette Configure Image Data (CID) command Render Alg orithm User Defined Dither Matrix Gamma Correction Color Lookup Tables View in g Illumin ant

As an exception, Monoch rome Pr in t Mode (?&b#M) immediately maps foreground c olor to its equivalen t gray. Similarly, deselection of Monochrome Pr in t Mode immediately returns foreground color to its color equivalent.

3-18 Using Palettes3-18 Using Palettes

Programming Color Palette s

Except for the default black and white palette or the Simple Color palettes (?*r#U), palette entries can be modified. The three primary compon en t s of a color are specif ied and the resulting color is assigned to the palette entry indicate d by ?*v#I.

In the explanation below, the term “compone nt” r efer s to the color space primary colors. For example, if the curr ent color space is CIE L*a*b*, compon ent 1 indic ates CI E L*, component 2 indic ates CIE a*, and compon en t 3 indic ates CIE b*.

Color Component

One

This command specifies the first primar y of the palette entry designated by the Assign Color Index comman d (?*v#I).

?*v#A

# = First Component

Default = 0

Range = –32767.0000 to 32767.0000 (up to 4 decimal places; command is ignor ed for invalid configuration s )

The Assign Color In dex co mmand actually applies this value and then resets it to 0.

Using Palettes 3-19Using Palettes 3-19

Color Component

Two

This command specifies the sec on d primar y of the palette entry designated by the Assign Color Index comman d.

?*v#B

# = Second Compon en t

Default = 0 Range = –32767.0000 to 32767.0000 (up to 4

decimal places; command is ignor ed for invalid configuration s )

The Assign Color In dex co mmand actually applies this value and then resets it to 0.

Color Component

Three

This command specifies the third primar y of the palette entry designated by the Assign Color Index comman d.

?*v#C

# = Third Compon en t

Default = 0 Range = –32767.0000 to 32767.0000 (up to 4

decimal places; command is ignor ed for invalid configuration s )

The Assign Color In dex co mmand actually applies this value and then resets it to 0.

3-20 Using Palettes3-20 Using Palettes

Assign Color Index This command assign s the thr ee curr en t color compon en t s

to the specified palette index number.

?*v#I

# = Index Number

Default = 0

Range = 0 to 2 bits per index (no assignmen t for out-of-r an g e values)

This command reset s the color componen ts to 0 after assignmen t. If th e specif ied ind ex number is greater than the palette size, no index assignment is made, but the three color componen t s are set to 0.

– 1, where n is the number of

Using Palettes 3-21Using Palettes 3-21

ModiM odifying Output Colorfying Output Color

Introduction The previous chap ter s of thi s manual have been concerne d

with giving an over vie w of th e color pr in ting pr oc es s, choosing co lor mod es, and using palettes. This por tion of the manual explains ho w color can be modified to pr odu c e a desired result, fro m using half ton e rende r alg orithms t o change the way color is render ed, to compensatin g for the yellow cast caused by a tungste n light source in a photograph . Th e HP co lor printers can modify colors usin g the following means:

Halftone render algorithms provide a way to modify images based on a dither cell con c ept. The algorithm chosen determines how specified colors are “rendered” as dots on the printed pag e.

Color lookup tables can remap palette colors to compensate for unw an ted color charac ter istic s of inpu t data. For example, if a scanned photog r aph had a reddish cast, a color lookup table cou ld be used to make the printed image look as if it were taken under a more balanced light so urc e.

Gamma correctio n prov ides a way to adjust for co lor differences in display monitors.

The Viewing Illuminant command allows you to vary the xy chromaticity coordinates for the light source under which you will be viewing a printed piec e. For example , if the printed doc ume nt is to be viewe d under a tun gsten light, the comman d modifies color s so that they have the correct appear anc e w hen illu minate d by a tungsten ligh t bulb.

The Monochrome Print Mode command con ve rts eac h color to its grayscale equiv alen t for faster, draft printing.

The Dr iv e r Config u r ati on command pr ovides a way for a driver to calibrate the output by adjusting color lightness, saturation, and color map information .

All of these methods of modifyin g outpu t co lor are explained in the follow in g section s.

Halftone Re nder Algorithms

Render Algorithm

Command

The HP color printers have the capability of applying different halfton e ren der algorith ms to achie ve the desired output on the printed image. Rende r algor ithms allow you to change the charac ter istics of the image by chang in g the way pixels are render ed. Each halftone render algorith m produces a different affect on the output, varying the texture and co lor appear ance of the printed image.

To choose the type of render in g to be used, use the Rend er Algorithm comman d, descr ibed below. This command allows you to choose one of the existing rendering algorithms or to choose a user -d efin ed patter n created with the Download Dithe r Matrix command .

The Render Alg orithm c omman d selec ts the alg orith m to b e used for rendering page marking entities on a given page.

?*t#J

# = 0 - Continuous tone

(device best dither) 1 - Snap to primaries 2 - Snap black to white and othe r color s

to black 3 - Device best dither 4 - Error diffusion 5 - Device best (monoc h rome) 6 - Monochrome error diffusion

4-2 Modifying Output Color4-2 Modifying Output Color

7 - Cluster order ed dither 8 - Monochrome cluster dith er 9 - User-defined dither

10 - Monochrome user-defined

1 1 - Ordered dither 12 - Monochrome ordered dither 13 - Noise ordered dither 14 - Monochrome noise ordered dither

Default = 3 Range = 0 to 14 (invalid values are ignored;

values 1 and 2 are ignored for device independent color)

Snapping to Primaries

This algorithm conver t s each compone nt of a color specification to its corresponding primary color. For example, assuming 8 bits per primary, an RGB input value greater than 128 snaps to 255; a value less than or equal to 128 snaps to 0.

Snapping Black to White

Choosing this option con verts black to white and all othe r colors to black. Input pr imary color s equal to a black specification are conve rte d to a white specific ation , an d other color specific ation s for the inpu t pr imarie s are converted to the black specification.

Device Best Dith er

This dither pattern produc es the best results for many images. Note, however, that the recommended dith er pattern varies with the image, the inten de d use of the image, and the subjectiv e judgeme nts of the user.

Error Diffusion

The input primaries of a given pix el (x,y ) are prin ted at the closest density available and the local error is propag ated to

M od ifying Output Color 4-3M od ifyin g O ut put Color 4-3

the unprinted ne ighbor ing pixels. Error diffu sion applie s only to raster data printe d using the Conf igu re Imag e Data command.

Ordered/ C lustered Dither

The ordered dith er or cluster order ed dith er causes a pix el to be intensified at a point (x,y) depen din g on the desired intensity, I(x,y), and on an n x n dither matrix, D, wher e

i = x modulo n j = y modulo n For RGB color spaces, if I(x, y) < D(i, j), the point

correspon din g to (x,y) is inten sified; other w ise it is not. The intensity of each primar y color is determin ed ac co rd ing to this scheme. The relationship betw een I and D depends on the specified color space.

Monochro me Ren dering

Monochrome render ing generates a gray value fr om the three primary colors. The gray value is compu ted accor din g to the NTSC standard, whic h for the Devic e RGB color space is:

Gray = 0.3 x Red + 0.59 x Green + 0.1 1 x Blue

Note Since it is impossible to characterize a printer for all

4-4 Modifying Output Color4-4 Modifying Output Color

User-Defined Dithering

For a user-defined dither, the input primaries are compared against differently dimen sion ed dith er s (e.g. MxN) , whic h may vary for each primary color.

possible dither algorith ms, rende r algor ithms 1, 2, 9 and 10 are not accessible when in a devic e-in dep enden t colo r spac e. If one of these render algo rith ms are selec ted whe n in a device-in de pen den t co lor space, the device best dither will be used instead.

User-Defined

Dithers

The Download Dither Matrix comman d ( ?*m#W) can create a dither matrix for one or all three primar y colors, in effect providing halftone screens. User-defined dither matrices can be used for optimizing the prin ter’s outpu t capabilities when using devic e-d epen de nt c olor spaces. They are ignored for device-independent color spaces, since the printer cann ot be calibr ated as is necessar y for device-in de pen den t co lor. User-defined half tones can be downloaded for each component of the color space.

A use r-d efin ed matrix is defined in additive color s (RGB values). The dither matr ix pixels are def ine d in term s of device-d epen de nt r esolu tion .

When using the Download D ithe r Matrix co mmand , you have several options:

You can choose whether to def ine a separate matrix for each color plane, or use the same matrix for all thr ee color planes.

You set the height and width of the dither cell. When using separate matr ic es for each plane , you can use different size dither cells for each plan e. For example, you can have a 4 x 4 pixel cell for red, a 4 x 6 cell for green, an d a 6 x 8 cell for blue.

You download the data bytes for each pixel of th e cell. Each data byte determin es a threshold—ever y pixel w ith a value greater than or equal to the thr esh old get s turned on and every pixel with a value less than the threshold does not get turned on.

M od ifying Output Color 4-5M od ifyin g O ut put Color 4-5

Download Dither

Matrix Command

The Download Dither Matr ix comman d specif ies a single matrix for all three primary color s, or thre e matric es (on e for each primary) , which may have diffe rent sizes and content s.

?*m#W[data]

# = Number of bytes of byte-alig ned binar y data

in the data field

Default = 0

Range = 7 to 32767 (command is ignored for

values of 0 – 6; values larger than 32767 or device limits are clamped; signs are ignored)

A dow nloade d user-define d dithe r will not take eff ec t unti l after explicitly selec tin g it via a render algo rith m co mmand with a value of 9 or 10. Howev er, if the current rende r algorithm (or l ast ren der algor ith m receiv ed ) was a user-defin ed alg or ithm (v alu e 9 or 10), then a user -def ine d matrix will take effect a s soon as it is downloaded. In thi s case, another ren der algorith m comman d (valu e 9 or 10) is not needed to “selec t” the dow nloaded user - defin ed dither matrix. This is due to the fact that the down load ed user-defin ed dith er algor ith m is the curren tly selecte d render algorithm.

If the command is sent before dow nloadin g a user -de fin ed dither matrix, the device will use the device’s user-defined dither default, if available , or, if no default is available, will use the default rend er algorith m.

Note The user-de fin ed dith er matrix must be defined for

4-6 Modifying Output Color4-6 Modifying Output Color

processing with additive colors (RG B).

Since user-d efin ed alg or ithms can not be used w he n a device-in de pen den t co lor space is active , try in g to specify a

user-defin ed alg or ithm in this situation cau ses the defau l t algorithm to be used. The defau lt is used until the algorithm is chang ed to somethin g other than user-define d, or until you spec ify a devic e-de pen den t co lor spac e.

The table below shows the format for a dither matrix that is applied to all three color primaries. The format for “multiple dither matrices” is supplied after this explanation. (“uint 16” means unsigned 16-bit integ er ; “ubyte” means unsigned byte.)

Byte 15 (msb) 8 7 (lsb) 0 Byte

0 Format = 0 Number of planes = 1 1 2 Dither matrix height in pixels (uint 16) 3 4 Dither matrix width in pixels (uint 16) 5 6 byte #0 (ubyte) byte #1 (ubyte) 7 8 byte #2 (ubyte) byte #3 (ubyte) 9

•

Format

This byte should be set to 0.

Number of Planes

This byte designates how many dither matrices are specified by the command. The co mmand is ignored an d the data discarded for any valu e other th an 1 or 3.

Byte Valu e Value Description

1 One matrix applied to all primaries 3 Each primary has a separate matrix

Height and Width

These bytes designate the size of the dither matrix in pixels. For example, a value of fou r for heig h t and six for width produces a dither cell that is four pixels wid e by six

M od ifying Output Color 4-7M od ifyin g O ut put Color 4-7

pixels high. Values must be non-zero and sized so the matrix contains no more than 32767 bytes. Other wise, the command is ignored and the data discard ed. The minimum dither matrix size is 1 x 1.

Data Bytes

After specify ing the heig ht and wid th of th e cell, data byte s are sent row-by- ro w (row-major ord er). Eac h data byte contains the normalized probabilities, ranging fro m 0 to 255, of one cell.

For example, a 2 x 2 cell could have no pixels prin t for RGB values of 205 through 255, one pixel for values of 153 through 204, two pixels from 101 through 152, three pixels for 49 through 100, and all four pixels betw een 0 and 48 (see the illustration below, which represents a halfton e cell for one of the primary colors—n ote th at the co lor data is in RGB values).

4-8 Modifying Output Color4-8 Modifying Output Color

Each dither matrix must be completely specifie d. Otherwise, the width an d heigh t values may be misinterpreted if multiple matric es are sent.

If the width, heigh t, and data specific ation s resu lt in an odd number data bytes, the next matrix specific ation will beg in on an odd byte boundary. No padding is provided for even-byte align in g .

Multiple Dither

Matr ices

As noted in the previous table, you set the number of plane s field to 3 to send separate matrices for each primary. Each dither matrix must have its own width and height data fields. As shown below, the matrix specification for each primary follows the previou s primar y colo r’s matrix specification .

Byte 15 (msb) 8 7 (lsb) 0 Byte

0 Format = 0 Number of

planes = 3 2 Dither matrix height in pixels (uint 16) 3 4 Dither matrix width in pixels (uint 16) 5 6 byte #0 (ubyte) byte #1 (ubyte) 7 8 byte #2 (ubyte) byte #3 (ubyte) 9

•

n Dither matrix height in pixels (uint 16) n + 1 n+2 Dither matrix width in pixels (uint 16) n + 3 n+4 byte #0 (ubyte) byte #1 (ubyte) n + 5 n+6 byte #2 (ubyte) byte #3 (ubyte) n + 7

•

m Dither matrix height in pixels (uint 16) m + 1 m + 2 Dith er matr ix width in pixels (uin t 16) m + 3 m + 4 byte #0 (ubyte) byte #1 (ubyte) m + 5 m + 6 byte #2 (ubyte) byte #3 (ubyte) m + 7

M od ifying Output Color 4-9M od ifyin g O ut put Color 4-9

Example This example produces a 4 x 4 dither matrix that is applied

to all three color primaries (the number of planes i s set to

1). The following command wou ld be sent to create this dither matrix:

?*m22W010404B0B1B2B3B4 . . . B15 (where the first 6 binary bytes ar e show n as ASCII h er e for clarity, and B1 . . . B15 indicate the binar y byte data).

The byte-aligned binary data field (shown a s ASCII for clarity) would be:

Byte 15 (msb) 8 7 (lsb) 0 Byte

00 1 1 20 4 3 40 4 5 6B0 B1 7 8B2 B3 9

•

20 B14 B15 21

Note Do not use downloaded dither matr ices as patter ns since

4-10 Modifying Output Color4-10 Modifying Output Color

the orientation of the patter n will not ro tate with chan ge s in orientation and page rotation.

Color Lookup T ables

Color lookup tables prov ide a way to re-map c olor data for the following types of applications:

Highlight an d shadow modific ation Saturation and desatu r ation Unique gamma correction curves Special effects for tonal correction Neutral balancing

Color lookup tables map input data for each primary color into a new output ran ge b ased on poin t-by -p oin t conversions. Color look up tables can modify input data for both device-dep en den t and dev ic e-in dependen t color spac es.

Like the CID command, the fir st byte of the data field identifies the color spac e to which the lookup tables will be applied. These tables specify on a point-per-p oin t basis a transformatio n from an inpu t space of 0 . . . 255 into an output space of 0 . . . 255. Figure 4-1 on the next page illustrates the concept.

The unit y looku p ta ble (see the following illustration) is the default for all color sp ace s; it perfo rms a 1:1 mapping of input to output (that is, 129 is mapped to 129). The inversion look up table perfo rms a simple color inversion ; for example, it inverts the red primar y of a device-dep en den t RGB color space to create cy an outpu t (fr om 255 red to 0 red, which is 255 cyan).

Color Lookup

Tables Command

This command enables and specifies colo r look up tables.

?*l#W[binary data]

# = Number of bytes of binar y da t a

Default = 0 Range = 0 or 770 (command is ignored for

other values; sign is ignore d)

Mod ifying Ou tp ut Color 4-11Mod ify ing Out put Col or 4-11

A value of 0 resets or initializes the color look up tables for each primary to the un ity c urv e (1:1). A value of 770 means the data for a color lookup table will be following . The command is ignored and the data is absorbed for any number of bytes not equal to 0 or 770.

4-12 Modifying Output Color4-12 Modifying Output Color

Fig ur e 4-1. Colo r L ooku p Tab l esFig ur e 4-1. Colo r L ooku p Tab l es

This command enables the color lookup tables un til an ?E, Configure Image Data (CID) , or anoth er Color Lookup T ables command with a 0 value field is received.

Note RGB gamma correction (?*t#I) and color lookup tables for

device-d epen de nt c olor spaces are mutu ally ex clusiv e and overwrite each other.

As shown below, the 256 point-by-point transfo rmatio n curve for each primary co lor is defined sequ en tially for a total of 768 bytes, with the additional 2 by tes for specify in g the color space and reser ved data field.

Byte 15 (msb) 8 7 (lsb) 0 Byte

0 Color Space Reser ved Data Field 1 2 Color Component 1, Index 1 Color Component 1, Index 2 3 4 Color Component 1, Index 3 Color Component 1, Index 4 5 . . . 256 Color Component 1, Index 255 Color Component 1, Index 256 257 258 Color Component 2, Index 1 Color Component 2, Index 2 259 260 Color Component 2, Index 3 Color Component 2, Index 4 261 . . . 512 Color Component 2, Index 255 Color Component 2, Index 256 513 514 Color Component 3, Index 1 Color Component 3, Index 2 515 516 Color Component 3, Index 3 Color Component 3, Index 4 517 . . . 768 Color Component 3, Index 255 Color Component 3, Index 256 769

Mod ifying Ou tp ut Color 4-13Mod ify ing Out put Col or 4-13

Byte 0 (Color Space)

Value Color Space

0 Device RGB (default) 1 Device CMY 2 Colorimetric RGB Spaces 3 CIE L*a*b* 4 Luminance-Chr omin ance Spac es

A color looku p table can be attach ed to on e or more of the color spaces anytime after a CID command . For examp le, a Luminance- Chr omin an ce space c an have four look up tables specified, namely:

Device-Depen dent space CIE L*a*b* space Colorimetric RGB space Luminance-Chrominance space

A r eset ( ?E), IN, or CID command sets each of the four levels of color lookup tables for eac h primar y to the unity curve.

4-14 Modifying Output Color4-14 Modifying Output Color

Gamma Correction Color monitors, whic h ar e by natur e non- line ar, appear

incorrect when given a linear ramp of some color. Gamma correctio n can significantly impr ove per ceptu al co rrec tn e ss by adjusting the brightness or darkness of the color data sent from the monito r to any other non-lin ear device .

Gamma Correction

Command ?*t#I

# = Gamma number

Default = 0 (gamma correction off) Range = 0.0 to 32767.0 (command is ignore d

for invalid values) * * The practical ran ge for gamma values is 0.0

to 4.0.

Assuming 8 bits per primary (256 inten sity levels per primary), the corr ec ted inte nsity for each color primar y is calculated as follows:

Intensity = ( (1 + log (input / 255) ) / gamma) * 255 Gamma correction is referred to in terms of device-

dependent RGB. This command does not destroy the content s of devic e-d epen de nt c olor looku p tables, but setting a gamma value supercedes any looku p table inp ut in either Device CM Y or Devic e RGB.

Note The default value (0) give s the same result as a gamma

value of 1.0, which results in a unity gamma curve.

Mod ifying Ou tp ut Color 4-15Mod ify ing Out put Col or 4-15

Viewing Illuminant

Printed color s und er go a hue shift wh en viewed u nd er different illuminations (for example, fluorescent, tungsten, or daylight). Colors with spec tral char ac teristics outside the range of an illumin ation sour ce are no t received, chan ging the appearan ce of mixed color s. Th e V iewing Illumin an t command (?*i#W) supports communication of standard illuminations to the prin ter to allow the prin ter to compensate for differ en t ligh tin g condition s wh en appearance match in g.

Viewing Illuminant

Command

The View ing Illuminan t co mmand specifie s the relativ e white point used in the determination of a viewing illuminant cond ition .

?*i#W[binary data]

# = Number of binary bytes o f da ta

Default = 8 Range = 8 (command is ignored for invalid

values; signs in the valu e field are ignor ed

The binary data field is formatted as follows:

Byte 15 (msb) 8 7 (lsb) 0 Byte

0 x chromaticity white poin t (l sw) 1 2 x chromaticity white poin t (m sw) 3 4 y chromaticity white poin t (l sw) 5 6 y chromaticity white poin t (m sw) 7

The above format adheres to the IEEE floatin g point for m at as follows:

4-16 Modifying Output Color4-16 Modifying Output Color

31 30 23 22 0

Sign Exponent Fractional Portion

The PCL default view in g illumin ant is D65 ( 6500K) . Below is a table of viewing illuminants and their chr omatic ity values.

Illuminant x chromaticity y chromaticity

Daylight (D65) (6500K) 0.3127 0.3290 T un gsten (3200K) 0.4476 0.4074 Cool White Fluorescen t

(5630K)

This command affects only devic e-in dependent colo r. The command acts like a state variable: it is ignored for White/Black, Dev ice RGB, or Device CMY palettes, but it becomes active when a new CID comman d specifies a device-in de pen den t co lor space.

0.3904 0.3914

Mod ifying Ou tp ut Color 4-17Mod ify ing Out put Col or 4-17

Monochr o me Printing

The Monochrome Print Mode command converts each color value to its grayscale equ ivale nt. This impr ove s throughpu t, costs less to print, and eliminates waste by providing a draft mode.

Monochrome Print

Mode Command

The Monochrome Pr in t Mode command desig nate s whethe r to print using the curren t rende ring mode or a fast gray-scale equ ivale nt. Page s prin ted usin g the gray -sc ale equivalen t do not use any color and th er efor e pr in t faster and more economically.

?&b#M

# = 0 – Print in mixed ren der algorithm mode

1 – Print using gray-scale equiv alen t

Default = 0 Range = 0, 1 (command is ignored for invalid

values)

This command must be sent prior to prin table data; otherwi se, the curr en t pag e is closed and pr in ted. It may be sent on a page-by-page basis.

4-18 Modifying Output Color4-18 Modifying Output Color

Driver Configur ation Command

device_id

function_index

This command specifies the Lig h tne ss, Saturatio n, and Scaling Algorithm to be applied to th e docu men t, an d allow s for the selection and dow nlo adin g of Color Map s.

?*o#W[device_id function_index Arguments]

# = Specifies the number of bytes to follow

(device ID + function index + argumen t s)

Default = N/A Range = see description below

Value Printer

6 Color LaserJet printer

function_

index

0 Lightness -100 to 100 1 Saturation -100 to 100 3 Scaling

Description Argument Range

0 Pixel Replic ation

Algorithm

1 Bilinear

2 Modified Bilinear

Mod ifying Ou tp ut Color 4-19Mod ify ing Out put Col or 4-19

Interpolation

function_

index

Description Argument Range

4 Select

Color Map

5 Download

Color Map

The following parag r aph s descr ibe the fu n ct ion_inde x values and their arg u ments.

0 No Adjustment 1 Process Blue 2 Vivid Graphics 3 Transparency 4 Out of Gamut 5 CIE Lab Match 1 CMY Color Space 3 CIELab Color Space See Ma pID List (14739 bytes)

Lightness Negative values darken (u nlig hten ) the image, text or

graphics colo r, but do not have any effec t on black or white data. Positive values lighte n the image. Zero tu rns the lightness adjustment off. This function index requires three data bytes.

Saturation Negative values desaturate (add gray to) the image, tex t or

Scaling Pixel replication is a backward-compatible scaling

4-20 Modifying Output Color4-20 Modifying Output Color

graphics colo r, but will not have any effect on black or white data. Positive values increase th e amount of saturation , making the image more vivid. Z er o turn s the satur ation adjustment off. This function index requir es thr ee data bytes.

algorithm. Bilin ear interpolation is a hig h- quality scaling algorithm for smo oth -edg e interpolated scaling. Modified bilinear scaling only inter polates wh en it is best to do so. This function index re quir es thr ee data bytes.

Select Color Map This value specifies which co lor treatmen t mode to use for

rendering the next job.

No Adjust ment

This setting provides linearization only (that is, the user sees the device as a linear dev ic e).

Process Blue

This setting provides the same results a s V ivid Gr aph ic s (linearization plus user-preferred enhancements) with the addition of mapping process blue, which looks sligh tly purple, to a blue closer to that of a standar d monitor.

Vivid Graphics

This setting adds color satur ation to the resultin g image.

T ra n sparency

This setting uses a map to render the best color output on transmissive media.

Out of Gamut

This setting prints colors in an imag e that are out of gamut—all colors that ar e in gamu t snap to white, all out-of-gamut color s are snap p ed to the gamut sur fac e. This setting only supports the dev ic e-in de pen den t co lor map.

CIE L*a*b* Match

This map performs a true color matc h to the requested CIE L*a*b* input (there are no appear anc e matchin g adjustments). This setting only sup por ts the devic eindependent color map.

Note For screen matchin g , the long for m of the Config ur e Imag e

Data command is used and the color maps are generated internally depe ndent upon the mon itor calibration data (the Driver Configuration command is not needed).

Mod ifying Ou tp ut Color 4-21Mod ify ing Out put Col or 4-21

Download

Color Map

The printer suppor ts the dow nloading of color adjustment maps dependent u pon the halfton e re que ste d, the type of color treatment desir ed (in clud ing devic e-de pen den t or independ en t), an d the type of media.

Setting Description MapID

Device Dependen t

No adjustment

Process Blue Cluster-Process Blue-DD 5

Transparency Cluster-Transparency-DD 9

Vivid Graphics

Out of Gamut

Cluster-No Adju st-DD 1 Disperse-No Adjust-D D 2 Scatter-No Adju st-DD 3 ErrorDif fusion-No Adju st-DD 4

Disperse-Process Blue-DD 6 Scatter-Pr oc es s Blue-DD 7 ErrorDiffusion-Process Blue-DD 8

Disperse-Transparency-DD 10 Scatter-Transparency-DD 11 ErrorDiffusion-Transparency-DD 12 Cluster-VividGraphics-DD 13 Disperse-VividGraphics-DD 14 Scatter-VividGraphics-DD 15 ErrorDiffusion-VividGraphics-DD 16 Cluster-OutOfGamut-DD 17 Disperse-OutOfGamut-DD 18

4-22 Modifying Output Color4-22 Modifying Output Color

Scatter-OutOfGamut-DD 19 ErrorDiffusion-OutOfGamut-DD 20

Setting Description MapID

CIELab Match

Device-Indep end ent

No Adjustment

Process Blue Cluster-Process Blue-DI 55

Transparency Cluster-Transparency-DI 59

Cluster-TrueMatch-DD 21 Disperse-TrueMatch-DD 22 Scatter-TrueMatch-DD 23 ErrorDiffusion-TrueMatch-DD 24

Cluster-No Adju st-DI 51 Disperse-No Adjust-D I 52 Scatter-No Adju st-DI 53 ErrorDif fusion-No Adju st-DI 54

Disperse-Process Blue-DI 56 Scatter-Pr oc es s Blue-DI 57 ErrorDiffusion-Process Blue-DI 58

Disperse-Transparency-DI 60 Scatter-Transparency-DI 61 ErrorDiffusion-Transparency-DI 62

Vivid Graphics

Out of Gamut

Cluster-VividGraphics-DI 63 Disperse-VividGraphics-DI 64 Scatter-VividGraphics-DI 65 ErrorDiffusion-VividGraphics-DI 66 Cluster-OutOfGamut-DI 67 Disperse-OutOfGamut-DI 68 Scatter-OutOfGamut-DI 69 ErrorDiffusion-OutOfGamut-DI 70

Mod ifying Ou tp ut Color 4-23Mod ify ing Out put Col or 4-23

Setting Description MapID

CIELab Match

Cluster-TrueMatch-DI 71 Disperse-TrueMatch-DI 72 Scatter-TrueMatch-DI 73 ErrorDiffusion-TrueMatch-DI 74

4-24 Modifying Output Color4-24 Modifying Output Color

The PThe PCL P rint ModelCL Print Model

Introduction The Print Model feature allow s images and char ac ter s to be

filled with color, with any of the printer’ s predefined shading or cros s-hatch patterns, or with a user-defined pattern. Images include any raster graph ic, such as one created with PCL raster gr aph ics commands (as describe d in Chapter 6, Raster Graphics); a rectangular fill area (as described later in this chapter a s PCL Rectangular Area Fill Graphics); or characters selec ted fr om any font.

Figure 5-1 illustrates the use of the prin t model. Th e following defin ition s are helpfu l in desc ribin g Prin t Model operation:

Figure 5-1.Figure 5-1. Prin t Mod e l Im agi ngPrint Model Imaging

The PCL Print Model 5-1The PCL Print Model 5-1

Pattern—The design which is “painted” through the non-white area of th e sour c e image onto the destination image. The pattern is defined by the Current Patte rn (?*v#T) command. It may be a color pattern or a single-plan e monoc hrome mask, suc h as the printe r’s internal pr ed efined shading or cr os s-hatch patterns, or a user-defined pattern. Foreground color is not applied to a user-defined color pattern.

When printin g a page, text and r aste r images are pr inte d using the current patte rn . Once the curren t patter n is specified, it stays in effec t un til an other is selected or the printer is reset. A reset retur ns the c urr ent patter n to it s default value (100% black ). The cur ren t patte rn does not always apply to rectan gular area fill, which uses patterns defined by th e rectan g ular area fill pattern commands.

Fore ground Color—Foreground color is selected from the current palette usin g the For egro und Color command (?*v#S). Foreground color affects everything except user-defined color patter n s an d HP-GL/2 primitiv es. Raster color mixes with fore groun d co lor (see Chapter 6 “Color Raster Graphics”).

Texture—Textu re is anothe r name for the combinatio n of pattern and fo re grou n d co lor, or for a color pattern which is not combined with a for eg r ound color.

Source Image—the Source Image is an image in which the non-white bits are replac ed by th e specif ied patter n . The source image func tion s like a stencil th roug h whic h the pattern is applied to the destination image . The source image may be one of the follo wing : HP-G L/2 primitives, rules, characte rs, or raster images (single plane mask or multi-plane color )

Destina ti on Im age— Th e image onto whic h the source image/texture combination is placed. The destination image includes any image s placed th ro ugh previo us operations.

Source Transparency Mode—The transparency or opaqueness of the source image’s “white” pixels as they

5-2 The PCL Print Model5-2 The PCL Print Model

are applied to the destination image (se e the note below ). Setting the source transpar en cy mode to 1 (opaque) applies the source image’s white pixels to the destinatio n image; with a setting of 0 (tran spar ent), th ese p ixe ls have no effect on the destination.

Pattern Transparency Mode— The tran spar en cy or opaqueness of the “wh ite pixe l s” in the pattern (see the note below). When set to 0 (transpar ent), these pix el s have no effect on the destin ation ; when set to 1 (opaque), they are applied throu gh th e black pixels of the sour ce pattern to the destination .

Logical Op era ti o ns —th e Pr int Model u se s logic al operations, suc h as AND, OR, X OR, an d NO T wh en determinin g whic h bits of the source, pattern , and texture beco me part of th e resultin g image. The Logical Operations command (?*l#O) can var y the log ic a l operation used, thus varying the outcome.

Note For RGB color imag es, “w h ite” p ixe ls are those for which all

color primaries are greater than or equal to their whit e referenc e values. For CMY color images, “wh ite” pixe l s are those for which all color primaries ar e less than or equal to their white reference values.

When usin g Ren der Algorithm 2 (?*t2J) for halftoning, black pixels are affected by the tran spar en cy mode in ste ad of white pixels.

For all renderin g algor ith m s, white dots intr odu ced in the dithering proc ess are not sub ject to tran spar en cy modes.

Figure 5-2 illustrates the effects of the sourc e and pattern transparenc y modes on the final image . (The transpar en c y modes work a little differently w ith rec tang u lar area fill—see “Pattern Transparency for Rectangu lar Are a Fill” near the end of this chapter.)

The PCL Print Model 5-3The PCL Print Model 5-3

This example uses the default ROP. The output may appear differently depending on the colors used.

Figure 5-2.Fig ur e 5-2. Opaq ue an d Tr ans p ar enc y Mo d esOpaq u e an d Tr an s p ar en c y Mo d es

Figure 5-3 demonstr ates the tr anspar en cy modes. In the first example (1a), the transparency mode for both the source image and the patter n is transp are nt. Since the source mode is “transpar ent,” on ly the non-w h ite re gio n (the circle) of th e sourc e image is over laid on the destination. Since th e patter n mode is also transparen t, the patterned source imag e is applied only to the white areas of the destination.

In the second example (1b), th e sour ce mode i s still “transparent,” but the pattern mode is “opaque” – so the pattern’ s white pix els are applie d to the destination . The resulting image shows the entir e circ le regio n vi sible and patterned.

In the third example (1c), the source mode is “opaque” and the pattern mode is transpar ent. Sinc e the source mode is opaque, the entire sour c e image (the cir cle and the surroundin g square) appear s overlaid on to the destination . The pattern, however, is allowed to pour through only onto the white-pixe led are a of the destination . The circ le is visible in the result, but only two opposing quarters appear patterned.

In the fourth example (1d), both source and pattern modes are “opaque.” The en tire source image is overlaid on to the destination, and the entir e circ le is pattern ed.

5-4 The PCL Print Model5-4 The PCL Print Model

HP (Hewlett-Packard) PCL 5 User Manual

Specifications and Main Features

Frequently Asked Questions

User Manual