HP (Hewlett-Packard) PCL User Manual

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PCL 5 Color Technical Reference Manual

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Inside This Manual

What You Can Learn From This Manual

This manual describes the PCL 5 commands used to print color on the HP Color LaserJet printer family and the other Hewlett-Packard PCL 5 color printers. Some of the main topics include an overview of the color printing process, using palettes, choosing color modes, adjusting output color to meet your requirements, printing color raster graphics, and HP-GL/2 vector graphics. Examples are provided which demonstrate the use of the PCL 5 color commands.

Note All commands described in this manual are not necessarily supported

by all printers. See the PCL 5 Comparison Guide for feature support information for each printer.

This manual is written primarily for users that are already familiar with PCL 5 printer features. For information on using PCL 5, see the PCL 5 Printer Language Technical Reference Manual.

iii

Manual Organization

This manual contains seven chapters and four appendices. Chapters 2 through 4 describe command usage for the HP Color LaserJet 4500 and 8500 printers. Appendices A through D describe how these functions are achieved on the HP Color LaserJet, Color LaserJet 5, 5M, and the DeskJet 1200C and 1600C printers. Chapters 5 through 7 pertain to all the color printers described in this manual. A brief description of each chapter is provided below.

Chapter 1. Color Printing Overview

This chapter explains background information about printing color documents using PCL 5. Topics include palettes, color selection, pixel encoding, color modes, and color matching.

Chapter 2. Using Color Modes

Chapter 2 defines the color modes and describes how to use them, including descriptions of sending color raster data using different pixel encoding modes and color spaces.

Chapter 3. Using Palettes

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

Chapter 4. Modifying Output Color

This chapter explains the options for modifying the output color: the Render Algorithm command, the Monochrome Print Mode command, Driver Configuration command, and Finish Mode command.

Chapter 5. The PCL Print Model

Chapter 5 describes the print model and how it determines the printed outcome when various patterns, colors, and images are applied together on a page. This chapter discusses the role that logical operations and transparency modes have on this process.

Chapter 6. Raster Graphics

This chapter describes the raster graphics commands and also compressing raster graphics images using various compression methods.

Chapter 7. Color Vector Graphics (HP-GL/2)

This chapter discusses printing color pages using HP-GL/2, the vector graphics language included on all PCL 5 printers. The chapter describes new and/or modified HP-GL/2 commands and how they are used to print with HP color print ers.

Appendix A. Color Printing Overview (Color LaserJet, 5, 5M, DeskJet)

Appendix A explains background information about printing color documents using PCL 5. Topics include palettes, device-dependent vs. device-independent color, color selection, pixel encoding, color modes, and color matching.

Appendix B. Using Color Modes (Color LaserJet, 5, 5M, DeskJet)

Appendix B defines the color modes for the HP Color LaserJet, Color LaserJet 5, 5M, and the DeskJet 1200C and 1600C printers, and describes how to use them. It includes descriptions of sending color raster data using different pixel encoding modes and color spaces.

Appendix C. Using Palettes (Color LaserJet, 5, 5M, DeskJet)

Appendix C describes the use of palettes for the HP Color LaserJet, 5, and 5M, and DeskJet 1200C and 1600C printers. It explains the palettes associated with the color modes and explains how palettes are created, saved, and modified.

Appendix D. Modifying Output Color (Color LaserJet, 5, 5M, DeskJet)

Appendix D describes how to modify output color for the HP Color LaserJet, Color LaserJet 5, 5M, and the DeskJet 1200C and 1600C printers. This chapter explains how color can be optimized by compensating for different conditions, such as variations in color due to light sources, limitations of the original artwork and variations in viewing monitors. The chapter details the use of halftone rendering algorithms, color lookup tables, gamma correction, and viewing illuminant commands. These commands are provided so that users can request and receive color output that matches their expectations.

Index

An index offers quick access to PCL command information.

Introduction

This chapter provides an overview of color printing with Hewlett-Packard printers. A primary goal for HP color printers has always been WYSIWYG (What You See Is What You Get) color, where the color displayed on the screen while creating a document is the same as the color in the printed document. However, this goal has been very difficult to realize due to a number of factors such as:

• Some colors that can be shown on a computer display cannot be reproduced by a printer.

• The Cyan, Magenta, and Yellow colors used to create the colors specified in a document can differ in hue and quality from printer to printer, even printers from the same manufacturer. Furthermore, the colors produced by a given printer can change over time, due to internal changes as well as temperature and humidity.

Until recently, these and other problems have led HP to approach color matching by presenting a PCL 5 color command set giving users the ability to make both major and minor color print quality adjustments.

However, the emergence of sRGB (standard Red Green Blue) as an international color data standard and the growing sophistication of Hewlett-Packard printers has allowed HP to provide high quality WYSIWYG color documents with a much simpler PCL color command set. Therefore, this manual has two main parts: Chapters 1 through 7 present the latest, simplified PCL 5 color command set, and the appendices describe the command set described in Chapters 1 through 4 as they are supported by the Color LaserJet, Color LaserJet 5, DeskJet 1200C, and DeskJet 1600C printers. Chapters 5 – 7 pertain to both sets of printers.

EN Color Printing Overview 1-1

Working with color documents

A document can be thought of as a series of text characters, vector graphics objects and images. The parts of a document either have color specifications in them, as do color images, or have color specifications applied to them, as do color vectors or text. For color images, the PCL 5 command set provides a way to specify the color format so that the image data can be interpreted correctly. For vector graphics and text, the PCL 5 color commands support the application of a color from a palette of colors.

Each color printed is synthesized from a combination of three colors: Cyan, Magenta, and Y ellow . The wa y the three colors are combined to produce the desired color is called a half-tone, and the PCL 5 color command, Render Algorithm, specifies which half-tone to use for a color. Advances in Hewlett-Packard printers have allowed HP to reduce the number of render algorithms to Best, High, and Low. While the actual implementation of each of these algorithms may vary from printer to printer, HP has determined that the three algorithms are sufficient to produce high quality color documents containing text and graphics.

The colors that appear on a page also have one of two color treatments applied to them:

1 Screen Match (sRGB), which provides the best WYSIWYG color.

This is the default color treatment.

2 The Vivid color treatment, which provides access to the entire

device gamut (range of colors the printer can produce). However , these colors are less correlated to those shown on a monitor than colors that have had the Screen Match treatment applied.

The following factors form the heart of the PCL color graphics state:

• The palette of colors to be used in a document

• The render algorithm to print the colors

• The color treatment to be applied to each color

Palettes of colors can be referenced by an ID, and so can PCL color graphic states. At any given time there is an active palette to apply colors from, along with a render algorithm and color treatment to be applied to the colors. Palettes and their associated render algorithm and color treatment can be stored and retrieved using a palette ID. When a palette is retrieved and made the active palette, the render algorithm and color treatment stored with the palette are set as the current render algorithm and color treatment.

1-2 Color Printing Overview EN

The PCL language also allows users to use patterns in combination with colors. These patterns and colors can be combined with text, vector graphics, and images to create new, complex graphics objects. The PCL Print Model determines the logical operations (known as ROPs, Raster Operations) used to combine each part of the graphic object.

PCL 5 Color Concepts

This section describes some of the concepts and terminology of color science related to the PCL 5 color commands.

Color

Color is a combination of human physiological and psychological responses to a relatively narrow band of frequencies in the electromagnetic spectrum. The frequencies visible to the human eye are called the visible spectrum. It’s useful to understand that color comes both from direct light and indirect light that has reflected from a surface. Reflected light absorbs all but the reflected frequency. The colors seen on a color monitor are combinations of different-colored lights traveling directly to the eye. They are called additive colors since the different colors combine to form the resulting color. The colors seen on a printed material such as paper are reflected from the paper surface, which absorbs some of the light. Colors seen under these conditions depend on the viewing conditions, the amount and color of ambient light, as well as the amount and color of the reflected light.

Color Specifications and Color Spaces

A given color can be described as particular amounts of three light frequencies (red, green, and blue light). For example, equal amounts of red, green, and blue light are perceived as white light. The absence of all three primary light colors is black.

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Color can be described in ways other than amounts of red, green, and blue light. Generally, these color specification systems are known as color spaces. For example, The Cyan, Magenta, Yellow (CMY) color space is us ed to descri be color s that ar e printed b y dep ositin g varyin g amounts of these three ink pigments (Cyan, Magenta, Yellow). The absence of pigment is considered to be white, and the presence of all three is black. The CMYK color space is similar to the CMY color space, but black pigment is used in place of 100% C, M, Y since imperfections in the hues of the C, M, Y pigments yield a dark brown rather than black.

A color specification, then, depends on the color space as well as the values used to describe a given color. Black in the RGB color space is described using the three numbers (0, 0, 0), but in the CMY color space it is described as (100, 100, 100), where the values are percentages of each color.

Color Management and the Standard Red, Green, Blue Color Space

For color to be reproduced in a predictable manner across different devices and materials, it has to be described in a way that is independent of the specific mechanisms and materials used to produce it. For instance, color displays and color printers use very different mechanisms for producing color. Traditionally, operating systems have supported color by declaring support for a particular color space (RGB in most cases). However , since the interpretation of RGB values varies between devices, color was not reliably reproduc ed across different devices.

The needs of the very high-end publishing sector could not be met by the traditional means of color support, so the various computer operating systems added support for using International Color Consortium (ICC) profiles to characterize device-dependent colors in a device-independent way. They used the profiles of the input device that created an image, and the output device that displayed or printed the image, to create a transform that moved the image from the color space of the input device to that of the output device. This resulted in very accurate color and access to the entire color gamut of both devices. However, it also involved the overhead of transporting the profile of the input device with the image and running the image through the transform.

1-4 Color Printing Overview EN

Note HP’s ICC profiles are available through normal HP software

distribution channels. For those who want the additional control available through building their own ICC profiles, there are several vendors of profiling tools available. To provide access to the printer's pure primaries and entire available printer gamut, the Vivid mode may be used when profiling the printer, and subsequently when using the ICC workflow.

However, there are a broad range of users that do not require this level of flexibility and control in an embedded color profile mechanism. Instead it is possible to define a single, standard default color space for exchange and interpretation of color data. Additionally , most existing file formats do not support color profile embedding, and may never do so. There is also a broad range of uses that actually discourages people from appending any extra data to their files. The sRGB color space addresses these issues.

The sRGB color space maintains the advantage of a clear relationship with ICC color management systems while minimizing software processes and support requirements. Since the image is in a known color space and the profile for that color space is included within the operating system and display application, this enables end-users to enjoy the benefits of color management without the overhead of larger files. Application developers and users who do not want the overhead of embedding profiles in documents or images should convert them to sRGB. While it may be that profiles buy slightly higher color accuracy, the benefits of using a standard color space far outweigh the drawbacks for a wide range of users. The migration of devices to support the standard color space (sRGB) natively will further enhance the speed and quality of the user experience.

The international standard color space sRGB (IEC 61966-2-1) is designed to complement current color management strategies by enabling a simple, robust method of handling color in the operating systems, device drivers and the Internet. This solution provides good quality and backward compatibility with minimum transmission and system overhead. Based on a calibrated colorimetric RGB color space well suited to cathode ray tube (CRT) displays, flat panel displays, television, scanners, digital cameras, and printing systems, the sRGB color space can be supported with minimum cost to software and hardware vendors. The four major technical components of the sRGB color space are the standard CRT primaries (HDTV P22 phosphors); the simple gamma value of 2.2, a D65 white point, and its well-defined viewing conditions.

EN Color Printing Overview 1-5

Palettes and Color Selection

The PCL 5 language allows the user to define a palette of colors. Each color is specified by three quantities or values which are interpreted depending on the color space. For example, the color white in an RGB palette is (1, 1, 1) while this set of values in a CMY palette defines the color black. Each color in the palette is accessed using an index number, starting with 0 as the first color in the palette. The largest palette holds 256 colors, which is approximately the largest set of distinct colors the human eye can distinguish under normal viewing co ndi tio ns.

A color from a palette can be applied to either text or vector graphics using the Foreground Color command. Once the command is invoked the selected color will be applied to all text and vector graphics page marking primitives, and to a certain extent to raster images.

Palettes can be identified with a Palette ID and then stored and recalled as needed. A palette stack mechanism is also supported for the convenience of applications that work well with a graphics stack.

PCL 5 Color Graphics Context

The Palette acts as the focal point of the PCL 5 color graphics context. The color space, render algorithm, color treatment, and pixel encoding mode are stored along with the palette. Therefore, selecting or restoring a palette also restores these values.

PCL 5 Color Mode

The PCL language has four modes or ways of specifying and using color:

• Black-and-White (monochrome) mode is the default mode so that backward compatibility with previous printers is maintained. When the printer is turned on it has a 2-entry palette containing the color white at index 0 and black at index 1. When the printer is reset with an mode.

• Simple Color mode is entered with the Simple Color command, which creates one of three fixed color palettes:

z A monochrome, two-entry palette with white at index 0 and

black at index 1.

1-6 Color Printing Overview EN

?E it reverts to this

z An RGB, eight-entry palette with the following colors

starting at index 0: black, red, green, yellow, blue, magenta, cyan, and white.

z A CMY, eight-entry palette with the following colors

starting at index 0: white, cyan, magenta, blue, yellow, green, red and black.

• PCL Imaging mode is entered with the Configure Image Data command that creates a programmable palette of a programmed size. This palette can be programmed using the color component and set index commands.

• HP-GL/2 Imaging mode is entered when HP GL/2 mode is entered and the initialize command IN creates a programmable palette that is shared between PCL and HP-GL/2.

Any and all of the modes can be used on a page. For example, you could enter the Simple Color mode to print a headline and bar chart, PCL imaging mode to print a photographic image, and Black-and-White mode for the text on the page. Each mode is described in more detail in Chapter 2. “Using Color Modes.”

PCL 5 Raster Images

Monochrome PCL 5 raster images are made up of a series of zeros and ones. A one indicates that a black dot should be deposited, a zero indicates no dot, letting the white background show through. A one-inch wide image with a resolution of 600 dots per inch (DPI) has 600 consecutive zeros and/or ones, which represent a horizontal slice through the image starting at the left edge of the image. This slice is known as a raster row. For an image one inch high and one inch wide, at 600 dpi there are 600 hundred rows of 600 zeros and/or ones. Color raster images follow the same conventions with this major exception: the representation of a dot is changed from a single zero or one to a color specification (a pixel).

Pixels and Pixel Encoding

Raster images can be thought of as being composed of a series of pixels (picture elements). In the case of monochrome raster images, a pixel is a single bit which takes on a value of zero or one. In color images a pixel is essentially a color specification. However, there are several ways of specifying a color, and how the color is specified is called the Pixel Encoding Mode (PEM).

EN Color Printing Overview 1-7

The PCL 5 color command set supports several Pixel Encoding Modes. The PEMs are categorized first by whether the pixel is an index into a palette, or a color specification. The other PEM categorization is whether the pixel data is divided into planes and transferred one plane at a time or is transferred in sequential order. There are four supported Pixel Encoding modes:

1 Indexed by Plane 2 Indexed by Pixel 3 Direct by Plane 4 Direct by Pixel (also known as 24-bit direct).

For example, the format known as direct by plane, uses a 3-bit pixel where the first bit indicates the presence or absence of a red dot, the second a green dot and the third a blue dot. The data is still arranged in rows, but all the red data is sent, then the green and finally all the blue. The example below represents the commands to transfer an image with the direct by plane PEM. The underlined bits, while transferred separately, are logically from the same pixel.

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

The direct by pixel PEM uses only the row transfer command. Each pixel is composed of three bytes, one byte per component of the color specification. All the bytes of a given pixel are transferred before the next one is transferred.

?*b#W row x b1 b2 b3 b1 b2 b3 b1...

The indexed by pixel PEM is similar to the direct pixel PEM but the pixel occupies at most one byte and is an index into the current palette.

The indexed by plane PEM is similar to the direct by plane PEM except the pixel's value is an index into the current palette. The use of this mode is discouraged due to the extra processing required to combine the bits from each plane into a single number, which is then used as an index into the current palette.

1-8 Color Printing Overview EN

Well-Behaved Raster

PCL raster images are processed most efficiently when the height and width of the image are specified before the Raster Start command begins an image data transfer. Furthermore, the entire image should be transferred before using the End Raster command to end the image. If the image is broken into pieces, certain print artifacts such as lines or squares can appear in the image. These can occur when “nearest neighbor operations” are applied to pixels that appear to be at the edge of an image, but are really inside an image that has been artificially broken up into smaller images.

EN Color Printing Overview 1-9

1-10 Color Printing Overview EN

Using Color Modes

Introduction

The PCL printer language has four color modes:

• Black-and-White

•Simple Color

• PCL Imaging

• HP-GL/2 Imaging

PCL allows you to use any mode or combination of modes to accomplish your printing objectives most efficiently.

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

Black-and-White Mode (Default)

Black-and-White Mode is the default color mode. PCL devices power up in this mode and revert back to it whenever the printer receives an

?E reset. Black-and-White mode is also selectable using the Simple

Color command ( 2-pen palette, with white at index 0 and black at index 1 (compatible with existing monochrome PCL 5 printers).

Simple Color Mode

Simple Color Mode, entered by the Simple Color command (?*r#U), creates a fixed-size, fixed-color, unmodifiable palette. Depending on the value field, 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.

EN Using Color Modes 2-1

?*r1U). This mode creates an unmodifiable, default

?*r#U can create a 2-pen Black-and-White palette,

PCL Imaging Mode

PCL Imaging Mode, enabled by the Configure Image Data command (

?*v#W), allows a maximum of 24 bits per pixel for color

specification. Therefore, more colors may be specified than are obtainable in Simple Color Mode. In the PCL Imaging Mode, pixel encoding mode, bits per pixel, bits per primary, and the color palette are all programmable.

HP-GL/2 Imaging Mode

In HP-GL/2, the Initialize (IN) command starts color imaging and performs the following:

• Sets the pixel encoding mode to index by plane.

• Sets bits per index to 3.

• Creates an 8-pen palette that is reprogrammable in either PCL or HP-GL/2 contexts (see Chapter 3, “Using Palettes,” for more information).

Although default HP-GL/2 palettes are different than default PCL palettes, an HP-GL/2 palette is modifiable in either PCL or HP-GL/2 (using the Assign Color Index [ respectively). Likewise, a PCL palette created by the Configure Image Data command ( using the same commands.

?*v#W) is modifiable in both PCL and HP-GL/2

?*v#I] or Pen Color [PC] commands,

The active palette is always transferred between HP-GL/2 and PCL contexts. Since only one palette at a time can be active, a new palette created in either context overwrites the current palette.

2-2 Using Color Modes EN

Simple Color Mode

The Simple Color command (?*r#U) specifies color 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#V command. In Simple Color mode, the pixel encoding 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 RGB palette

Default =1

Range =–3, 1, 3

?*b#W command; all other planes are sent using the

This command destroys the active palette and creates a new palette, which becomes the active palette. When the Simple Color mode is active, PCL and HP-GL/2 commands that modify the palette are locked out (NP, PC, Color palette is popped from the stack ( modified, and the pixel encoding mode reverts to indexed planar.

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

• 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 Device CMY color space.

EN Using Color Modes 2-3

?*v#A, ?*v#B, ?*v#C, ?*v#I). When a Simple

?*p#P), it cannot be

The Simple Color palettes are structured as follows:

Single Plane (value = 1)

Index Color

0White 1Black

3-Plane RGB (value = 3)

Index Color

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

3-Plane CMY (value = –3 )

Index Color

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

2-4 Using Color Modes EN

PCL Imaging Mode

The PCL Imaging mode, entered using the Configure Image Data (CID) command ( palette. It provides multiple color spaces, pixel encoding modes, and reprogrammable palettes.

Configure Image Data (CID) Command

The CID command provides configuration information for creating palettes and transmitting raster data. The CID command performs the following:

• Designates the color space for the newly created palette

• Designates the size of the palette

• Designates the Pixel Encoding Mode, the format of the raster data

• Designates, in certain circumstances, the size, in bits, of the three components of the color specifications. However, this information is rarely useful since it applies only to the direct-by-pixel PEM, where the format must be eight bits per component for 24-bit direct color, and the direct-by-plane, where there is one bit per component.

?*v6W b0 b1 b2 b3 b4 b5

?*v#W), creates a variable-sized programmable

Where:

6 = The number of bytes following the “W” b0 = byte 0 The color space b1 = byte 1 The Pixel Encoding Mode b2 = byte 2 The number of bits per index which implies the

size of the palette

b3 = byte 3 The number of bits in color component

(primary) #1

b4 = byte 4 The number of bits in color component

(primary) #2

b5 = byte 5 The number of bits in color component

(primary) #3

EN Using Color Modes 2-5

The bytes are ordered as follows and are unsigned bytes:

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

0 Color space Pixel encoding mode 1 2 Bits/index Bits/primary #1 3 4 Bits/primary #2 Bits/primary #3 5

Invalid configurations of the CID command are ignored and the data discarded. A minus or a plus sign in the value field (-6 or 6) is ignored

The data fields in the command, bytes zero to five, must contain byte-aligned binary data, not ASCII data.

Byte 0 (Color Space)

This byte specifies the color space. The range of values is 0 through

2. All other values are ignored.

Byte Value Color Space

0 Device Dependent RGB (default) 1 Device Dependent CMY 2 Standard RGB (sRGB)

Color space 2, sRGB, was the designation for Colorimetric RGB in the Color LaserJet an d C ol or L aserJet 5 print er s. The v alu e 2 i s us ed to represent sRGB since it is analogous to a standardized Colorimetric RGB and the intent of the two color spaces is the same.

2-6 Using Color Modes EN

Byte 1 (Pixel Encoding Mode)

This byte designates the format of any subsequent raster images. The range of the value is zero to three. All other values for this field are ignored.

V alue Pixel Encoding

Restrictions

Mode

0 Indexed by Plane Bits/Index can only be 1, 2, 3, 4, 5, 6,

7, or 8. Bit/Components 1, 2, and 3 are ignored

1 Indexed by Pixel Bits/Index can only be 1, 2, 4, or 8.

Bit/Components 1, 2, and 3 are ignored

2 Direct by Plane Bits/Components 1, 2, and 3 must

be 1

3 Direct by Pixel Bits/Components 1, 2, and 3 must

be 8

The number of bits per index determines the size of the palette created by this command. In the case of the Indexed by Plane mode the number of planes needed to represent the index is also determined by the number of bits per index. Therefore, if a 256 entry palette is needed, then the bits per index is set to eight since

= 256. If the Indexed by Plane mode is chosen, at most eight

planes are needed to represent each row of data. The recommended pixel encoding mode is Direct by Pixel, since this

gives the most efficient raster processing. However, using this mode means that delta row compression should be used since it exploits redundancy between rows. Other PCL compression modes exploit redundancy within a row. With Direct by Pixel the redundancy from pixel to pixel in a row is masked by the differences at the byte level within the pixel, that is, the differences between the red, green, and blue bytes within the pixel.

Note Raster data in Index by Plane or Direct by Plane modes cannot be

compressed using raster compression mode 5.

You need one plane or one bit/pixel for each power of two colors in the palette. For example, a 256-color palette requires 8 planes or

8bits/pixel (2

EN Using Color Modes 2-7

= 256).

PEM 0: INDEXED BY PLANE In Pixel Encoding Mode 0, successive planes of data are sent for

each raster row. A plane contains one bit for each pixel in a row. A pixel is not fully defined until all the planes for that row have been received, which is signaled by a transfer raster row command. The planes in a row form index numbers into the current palette. For example, assuming three bits per index, the underlined column of bits in the figure below is the palette index for pixel three of the first row (i1 is the least significant bit, i3 is the most significant bit). Note that the Transfer Raster Data by Plane command ( planes except the last plane of each row, which is sent using the Transfer Raster Data by Row command (

?*b#V) is used for all

?*b#W).

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

Example:

In the example below, the row transfer commands are shown in binary for clarity, even though the actual data would be byte-aligned binary data. The example is for an eight-pixel-wide image.

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

in hex. This command sets the color space to RGB, the PEM to Indexed by Plane, the palette size

to 8 (2 ignored.

). The last 3 bytes are

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

each pixel in the first row).

?*b1V01110000 Transfer plane 2 (the second bit

for each pixel in the row).

?*b1W10101000 Transfer plane 3 (the third and

final bit for each pixel in the row) and move to the next row. Note that the used to send the last plane of each row.

2-8 Using Color Modes EN

?*b#W command is

PEM 1: INDEXED BY PIXEL In this mode, each pixel in a row is fully specified before any bits are

sent for the next pixel. The bits for each pixel form a palette index number. Assuming four bits per index, the underlined block below is the palette index for pixel two of row one (i1 is the least significant bit).

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

Example:

In the example below the data in the row transfer commands are shown as two-digit hexadecimal numbers for clarity, even though the actual data would be byte-aligned binary data. The example is for a two-pixel-wide image.

?*v6W 00 01 04 08 08 08 Binary Data for the CID

command represented in hexadecimal. This command sets the color space to RGB, the PEM to Indexed by Pixel, the palette size to 16 (2 three bytes are ignored.

). The last

?*r1A Start raster ?*b1W45 The most significant nibble

selects palette entry 4 for the first pixel. The second pixel is set to index 5. Move to next row.

?*b1W6A The first pixel is index 6, the

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

?*b1W03 The first pixel is index 0, the

second pixel is index 3.

EN Using Color Modes 2-9

MODE 2: DIRECT BY PLANE In this mode, a pixel is composed of three, one-bit components. The

data is transferred a plane at a time, one plane for each component. Therefore, each bit in a plane represents one component of a pixel. The underlined bits below show the components for a pixel.

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

Example:

In the example below the data in the row transfer commands are shown in binary for clarity, even though the actual data would be byte-aligned binary data. The example is for an eight-pixel-wide image.

?*v6W 00 02 01 01 01 01 Binary Data for the CID command

represented in hexadecimal. This command sets th e co lo r sp ac e to RGB, the PEM to Direct by Plane. The palette size is ignored. The last three bytes are always one for this mode.

?*r1A Start raster ?*b1V10110000 Transfer plane 1 (the first bit for

each pixel in the first row). Each bit controls the red primary.

?*b1V01110000 Transfer plane 2 (the second bit

for each pixel in the row). Each bit controls the green primary.

?*b1W10101000 Transfer plane 3 (the third and

final bit for each pixel in the row) and move to the next row. Each bit controls the blue primary. Note that the used to send the last plane of each row.

2-10 Using Color Modes EN

?*b#W command is

MODE 3: DIRECT BY PIXEL This mode specifies a pixel as three, eight-bit components, thus the

name 24-bit direct color. Assuming the RGB color space with the mandatory eight bits per component, the underlined bytes below define the first pixel of row two.

?*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 . . .

Example:

?*v6W 00 03 00 08 08 08 Binary Data for CID command

represented in hexadecimal. This command sets the color space to RGB, the PEM to Direct by Pixel. The palette size is ignored. The last three bytes must be 8.

?*r1A Start raster ?*b3W 45 06 30 The three bytes specify a single

pixel. The first sets 45 as the red component’s value, the second sets the green value to 06, and the third sets the blue value to

30.

Byte 2 (Number of Bits per Index)

This command creates a palette regardless of the PEM chosen. This byte determines the size of the created palette. The palette size is two raised to the power of n (2

• In the Indexed-by-Plane PEM, where the raster data is interpreted as palette indices, this value determines the number of planes required per row.

EN Using Color Modes 2-11

), where n is the bits per index.

• In the Indexed-by-Pixel PEM, where the raster data is interpreted as palette indices, this value determines how to interpret the byte-ordered row transfers. The following list shows ho w each byte is translated into indices:

Bits/Index Indices/Byte

18 24 42 81

• In the Direct-by-Plane and Direct-by-Pixel PEMs, byte 2 does not apply to the raster format.

Bytes 3, 4, and 5 (No. of Bits for Components 1, 2, and 3)

These bytes are ignored for the Indexed by Plane and Indexed Direct PEMs. For the Direct by Plane PEM they must be set to one bit per component. For the Direct by Pixel PEM, they must be set to eight bits per component.

2-12 Using Color Modes EN

HP-GL/2 Imaging Mode

The HP-GL/2 Imaging Mode provides a way of using vector commands in printing documents. Although the default PCL and HP-GL/2 palettes are not the same, when transferring from PCL to HP-GL/2, active palette information does stay the same. You can switch between PCL and HP-GL/2 and use the same palette, and you can also modify palettes using either PCL or HP-GL/2.

Compared to monochrome printers, the HP Color LaserJet printer family, DeskJet 1200C and 1600C color printers have some commands that are new and/or modified for use with color printers. Chapter 7 describes the new or modified HP-GL/2 commands.

If you are not familiar with using HP-GL/2, see the PCL 5 Printer Language Technical Reference Manual. It provides a detailed explanation of using HP-GL/2.

EN Using Color Modes 2-13

2-14 Using Color Modes EN

Using Palettes

Introduction

A palette is a collection of color specifications selected using index numbers. The figure below illustrates a palette. Each palette entry associates an index number with three primary color components. For HP-GL/2 purposes only, a pen width is also associated with each palette entry.

EN Using Palettes 3-1

In non-raster mode, the current palette contains all the available colors. In raster mode, indexed color selection uses the palette, but direct selection does not.

Default palettes are created by all the PCL color modes (Black and White, Simple Color, PCL Imaging, and HP-GL/2 Imaging). The active palette may be modified when in the PCL Imaging or HP-GL/2 imaging 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 the 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 context remains active and unchanged when switching to the HP-GL/2 context, and a palette created in the HP-GL/2 context remains active and unchanged when switching to the PCL context. Performing a reset or entering PJL overwrites the active palette with the default black and white palette.

Whenever a new palette is created, the currently or previously active palette is destroyed. A new palette is created by power-on and also by the following commands:

• PCL Reset (

•Simple Color (

• Configure Image Data (

• HP-GL/2 Initialize (IN)

The active palette can be saved by pushing it onto the palette stack with the Push/Pop Palette command ( the stack destroys the active palette—the popped palette becomes the active palette.

?E)

?*r#U)

?*v#W)

?*p#P). Popping a palette from

3-2 Using Palettes EN

Saving the Palette

The current palette is destroyed when a new palette is created. The Push/Pop Palette command ( palette and then restore (pop) it.

Push/Pop Palette Command

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

?*p#P

# = 0 - Push (save) palette

1 - Pop (res t o re) palette

Default =0

Range = 0, 1 (invalid values are ignored)

?*p#P) can save (push) the current

A value of 0 ( palette stack. When a palette is pushed, the active palette is not affected.

A value of 1 ( destroys the active palette; the popped palette becomes the active palette. As with any stack, the last item pushed is the first item popped.

Pushing a palette saves the following parameters:

• Color definitions for each palette entry

• Pen widths (for HP-GL/2 use)

• Color space specification

• Number of bits per index

• Pixel encoding mode

• Number of bits per primary

• Color treatment

• Render algorithm

?*p0P) pushes a copy of the active palette onto the

?*p1P) pops the most recently pushed palette and

EN Using Palettes 3-3

Pushing a palette does not save the following parameters.

• 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-memory error. Attempts to pop from an empty stack are ignored.

Macros can push and pop palettes. A palette that was popped in an executed macro remains in effect at the end of the macro (this is not true for “called” or “overlaid” macros).

The PCL reset command ( empty the palette stack and overwrite the active palette with a non-programmable black and white palette. The HP-GL/2 commands 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.

?E) or an exit to PJL causes the printer to

3-4 Using Palettes EN

Palette Management by ID

All palettes have a unique ID (identification number). The default black and white palette created on power-up or

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/Pop Palette command; the store holds palettes having palette IDs.

?E has an ID of 0.

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 store. A palette popped from the stack goes into the palette store, becomes the new active palette, and assumes the ID of the previously active palette, which is overwritten. Only one palette at a time may be active.

EN Using Palettes 3-5

Management by ID allows applications to tag data, have multiple raster configurations, and have palettes for different color spaces—all without reconfiguring the active palette. For example, one palette can be created for PCL text, one for HP-GL/2 prim iti ves, one for simple raster, and one for 24-bit raster. The application can then switch between palettes according to what is being sent to the printer.

Selecting a new active palette changes the PCL graphics state. Besides the color entries, a palette also has the graphics state which contains the color space, color treatment, and render algorithm. This ensures that the same color specification in a given palette will always produce the same printed color.

As described below, the Select Palette ( (

?&p#C), and Palette Control ID (?&p#I) commands implement the

three basic operations of management by ID.

• Selection of the active palette

• Deletion of palettes

• Copying of palettes

?&p#S), Palette Control

Select Palette Command

The Select Palette command selects a new active palette by specifying an ID number. The previously active palette is 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 specified 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 for the duration of the print job, or until another Select Palette command is received.

This command can be used to de-select the active palette and select as the new active palette a palette created by the Palette Control command ( of 44 and select the new palette to use or modify, send

?&p#C). For example, to copy the active palette to an ID

?&p44i6c44S.

3-6 Using Palettes EN

When a palette creation command is received such as Configure Image Data ( created palette overwrites the active palette and is assigned the current palette select ID.

A palette popped from the stack overwrites the active palette, and is assigned the current palette select ID.

?*v#W), Simple Color (?*r#U), or an HP-GL/2 IN, the

?E resets the palette select ID value to 0 and deletes all palettes in

the palette stack and palette store, including the active palette, which is replaced by a default PCL fixed black and white palette with a palette ID of 0.

Macros affect the palette select ID value as follows:

• Calling or Overlaying a macro—saves the ID value and a copy of the active palette. Upon macro exit, the restored palette again becomes the active palette with the restored ID. An existing palette with this ID is deleted.

• Executing a macro—does not save the ID value or the active palette; changes remain in effect.

EN Using Palettes 3-7

Palette Control ID

The Palette Control ID command specifies 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

The ID number specified by this command is saved as the palette control ID and is used by the Palette Control command (

?E or power-up resets the palette control ID to 0, which is then the

default black and white palette ID. Macros affect the palette control ID value as follows:

• Calling a macro—saves the value and restores the value at exit.

• Exec ut i ng a ma c ro— d o es no t save the value; cha n ge s rem a in in effect at exit.

• Overlaying a macro—copies the value before resetting to 0, and restores at exit.

values)

?&p#C).

3-8 Using Palettes EN

Palette Control

The Palette Control command provides a mechanism for making and deleting palettes.

?&p#C

# = 0 - Delete all palettes except those in the stack (active

1 - Delete all palettes in the stack (active palette is not

2 - D ele te pale tte (spe ci fie d 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 value of 0 deletes all palettes except 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 value of 1 clears the palette stack. The active palette is unaffected, and the palette control ID is not used.

• A value of 2 deletes the palette with the specified palette control ID if it exists; otherwise the command is ignored. For example, to delete palette 53, send palette's ID is specified the active palette is replaced by the default black and white palette. This option does not change the palette control ID value.

palette deleted)

affected)

?&p53i2C. If the active

Note When the active palette is replaced by the default black and white

palette, the graphics state associated with the previous palette is also replaced.

• A value of 6 creates a copy of the active palette. The copy receives the ID specified by the last Palette Control ID command. For example, to copy the active palette to a palette with an ID of 14, send overwrites any palette that already has an ID equal to the palette control ID. The copied palette does not become the active palette. The command is ignored if a palette is to be copied to its own ID.

EN Using Palettes 3-9

?&p14i6C. The copied palette

The Palette Control command provides a way of managing system memory by deleting palettes in either the stack or store that are no longer in use.

Palette Control that is exercised during macros can have significant impact on palettes that exist within the system. Deleting all palettes, or those on the stack, or the current palette, or all those except on the stack can have adverse effects when the macro is exited. The adverse effect could be the deletion of the desired palette, and replacement with a black and white non-programmable palette.

3-10 Using Palettes EN

Simple Color Palettes

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

The Simple Color command overwrites the current palette with one of the fixed palettes below. When the Simple Color command is in effect, the PCL and HP-GL/2 commands that modify a palette entry (NP, PC,

?*v#A, ?*v#B, ?*v#C, ?*v*I, ?*t*I) are locked out. A popped

simple color palette cannot be modified and the pixel encoding mode reverts to “index by plane”. Only the IN or the CID ( commands can create a modifiable palette.

?*v#W)

As shown below, a value field of 1 ( palette. A value of 3 creates an 8-pen palette in Device RGB color space. A value of –3 creates an 8-pen palette in Device CMY color space. All of these Simple Color palettes are fixed and non-programmable.

?*r1U) creates a black and white

Single Plane (value = 1)

Index Color

0White 1Black

3-Plane RGB (value = 3)

Index Color

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

EN Using Palettes 3-11

3-Plane CMY (value = –3 )

Index Color

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

3-12 Using Palettes EN

CID Color Palettes

The Configure Image Data command, explained 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 reassigned a different color using PCL commands (

?*v*I) or HP-GL/2 commands (PC, NP). Default palettes vary by

color space.

Device RGB and sRGB Palettes

Bits/Index = 1

Bits/Index = 2

?*v#A, ?*v#B, ?*v#C,

Index Color

0White 1Black

Index Color

0Black 1Red 2Green 3White

Bits/Index = 3 through 8

Index Color

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

n > 7 Black

EN Using Palettes 3-13

Device CMY Palettes

Bits/Index = 1

Index Color

0White 1Black

Bits/Index = 2

Index Color

0White 1Cyan 2 Magenta 3Black

Bits/Index = 3 through 8

Index Color

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

n > 7 Black

3-14 Using Palettes EN

HP-GL/2 Palettes

Regardless of the color space, a default PCL palette is always different than a default HP-GL/2 palette. The following table shows the default palettes established in HP-GL/2. Like a default CID palette, a default HP-GL/2 palette can be modified in either PCL or HP-GL/2 contexts using the following commands:

PCL

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

• Assign Color Index (

HP-GL/2

• Number of Pens (NP)

• Pen Color Assignment (PC)

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

T wo Pens

?*v#I)

Pen Number Color

0White 1Black

Four Pens

Pen Number Color

0White 1Black 2Red 3Green

EN Using Palettes 3-15

Eight Pens

Pen Number Color

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

n > 7 Black

3-16 Using Palettes EN

Foreground Color

All PCL marking entities utilize “foreground” color, which is selected from the current palette using the Foreground Color command (

?*v#S). Foreground color interacts with raster color depending on

the print model commands in effect.

Foreground Color Command

The Foreground Color command sets the foreground color to the specified index of the current palette.

?*v#S

# = Index number into current palette

Default =0

Range = 0 to 2

Specified values that are out-of-range of the current palette are mapped into a new index as follows:

Index = Specified foreground index modulo palette size

(current palette size)

– 1

For example, specifying a foreground color index of 10 when 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 index is mapped according to the HP-GL/2 mapping function.

Foreground color affects the following PCL page marking primitives:

• Text characters (they change to the foreground color, including underlining)

• Solid or monochrome patterned rectangular area fills (rules)

• Monochrome patterns (except HP-GL/2)

• Raster images

The following are not affected:

• User-defined color patterns (format 1 download patterns)

• HP-GL/2 marking primitives (HP-GL/2 uses “selected pen”, but ignores foreground color)

EN Using Palettes 3-17

Note Foreground color interacts with color raster images. In the printer, all

color raster is resolved into three binary raster planes of CMY. Foreground color is applied to these planes, modifying the color image. For no interaction, set foreground color to black when sending color raster images.

After a foreground color is selected, changing any of the following will not change foreground color until a new Foreground Color command

?*v#S) is issued:

(

• Activ e Palette

• Configure Image Data (CID) command

• Render Algorithm

3-18 Using Palettes EN

Programming Color Palettes

Except for the default black and white palette or the Simple Color palettes ( components of a color are specified and the resulting color is assigned to the palette entry indicated by

In the explanation below, the term “component” refers to the color space primary colors. For example, if the current color space is sRGB, component 1 indicates R, component 2 indicates G, and component 3 indicates B.

Color Component One

This command specifies the first component of the palette entry designated by the Assign Color Index command (

?*v#A

Default =0

Range = –32767.0000 to 32767.0000 (up to 4 decimal places;

?*r#U), palette entries can be modified. The three primary

# = First Component

command is ignored for invalid configurations)

?*v#I.

?*v#I).

The Assign Color Index command actually applies this value and then resets it to 0.

Color Component Two

This command specifies the second component of the palette entry designated by the Assign Color Index command.

?*v#B

# = Second Component

Default =0

Range = –32767.0000 to 32767.0000 (up to 4 decimal places;

command is ignored for invalid configurations)

The Assign Color Index command actually applies this value and then resets it to 0.

EN Using Palettes 3-19

Color Component Three

This command specifies the third component of the palette entry designated by the Assign Color Index command.

?*v#C

# = Third Component

Default =0

Range = –32767.0000 to 32767.0000 (up to 4 decimal places;

command is ignored for invalid configurations)

The Assign Color Index command actually applies this value and then resets it to 0.

Assign Color Index

This command assigns the three current color components to the specified palette index number.

?*v#I

# = Index Number

Default =0

Range = 0 to 2

This command resets the color components to 0 after assignment. If the specified index number is greater than the palette size, no index assignment is made, but the three color components are set to 0.

3-20 Using Palettes EN

– 1, where n is the number of bits per index (no

assignment for out-of-range values)

Modifying Output Color

Introduction

The previous chapters of this manual have been concerned with giving an overview of the color printing process, choosing color modes, and using palettes. This portion of the manual explains how color can be modified to produce a desired result, from using halftone render algorithms to change the way color is rendered, to selecting a color treatment and finish mode. The HP color printers can modify colors using the following means:

• Halftone render algorithms provide a way to modify images based on a dither cell concept. The algor ith m chosen determines how specified colors are “rendered” as dots on the printed page.

• The Monochrome Print Mode command converts each color to its grayscale equivalent for faster, draft printing.

• The Driver Configuration command provides a way to select a color treatment.

• The Finish Mode command allows the user to specify the finish, matte or glossy, to be applied to the document.

All of these methods of modifying output color are explained in the following sections.

EN Modifying Output Color 4-1

Halftone Render Algorithms

The HP color printers have the capability of applying different halftone render algorithms to achieve the desired output on the printed image. Render algorithms allow you to change the characteristics of the image by changing the way pixels are rendered. Each halftone render algorithm produces a different affect on the output, varying the texture and color appearance of the printed image.

To choose the type of rendering to be used, use the Render Algorithm command, described below.

Render Algorithm Command

The Render Algorithm command selects the algorithm to be used for rendering page marking entities on a given page.

?*t#J

# = 0 - Continuous tone detail (high lpi) (device best dither)

3 - Device best dither 15 - Continuous tone smooth (high lpi) 18 - Continuous tone basic (low lpi)

Default = 3

Range = 0, 3, 15, 18 (invalid values are ignored)

Device Best Dith er

This dither pattern produces the best results for many images. Note, however, that the recommended dither pattern varies with the image, the intended use of the image, and the subjective judgements of the user.

4-2 Modifying Output Color EN

Monochrome Printing

The Monochrome Print Mode command converts each color value to its grayscale equivalent. This improves throughput, costs less to print, and eliminates waste by providing a draft mode.

Monochrome Print Mode Command

The Monochrome Print Mode command designates whether to print using the current rendering mode or a fast gray-scale equivalent. Pages printed using the gray-scale equivalent do not use any color and therefore print faster and more economically.

?&b#M

# = 0 - Print in mixed render algorithm mode

1 - Print using gray-scale equivalent

Default =0

Range = 0, 1 (command is ignored for invalid values)

This command must be sent prior to printable data, or it is ignored. The command must be sent at the start of a job, since few, if any, applications support a mixture of color and monochrome printing of color images within the same document.

EN Modifying Output Color 4-3

Driver Configuration Command

This command specifies the color treatment applied to each color specification.

?*o#W[device_id function_index Arguments ]

# = Specifies the number of bytes to follow (device ID

function index arguments)

Default =N/A

Range = see description below

device_id

Value Printer

6 Color LaserJet printer family 8 Color LaserJet 4500 printer

function_index

function_

index

4Select Color

The following paragraphs describe the function_index values and their arguments.

Description Argument Range

3 Vivid Graphics

Treatment

6 Screen Match

Select Treatment

This value specifies which color treatment mode to use for rendering the next job.

Vivid Graphics

This setting adds color saturation to the resulting image, and provides access to the full gamut of the printer (at the cost of color matching).

4-4 Modifying Output Color EN

Screen Match

Due to the emergence of sRGB (standard Red Green Blue) as an international color data standard, there is no longer a need to provide color adjustments in the printer driver to account for alternate types of RGB data. sRGB is the native color space of monitors, the default color space of the World Wide Web, the default space of many digital cameras and scanners. This treatment indicates that the printer should be ready to accept sRGB data. This is the preferred mode of operation to provide a good appearance match between the monitor and the printed document

The table below lists the driver configuration commands for both color treatments:

Note The device_id and function_index arguments after the ?*o3W (such

as 643) should actually be entered as ASCII-coded decimal. For example, instead of 643 you would actually enter the ACK control code, followed by the EOT and ETX control codes.

Treatment Command

LJ 4500 Other Color LaserJet

Famil y printers

Vivid Graphics Screen Match

EN Modifying Output Color 4-5

?*o3W843 ?*o3W643 ?*o3W846 ?*o3W646

Finish Mode Command

The Finish Mode command allows the user to specify the finish, matte or glossy, to be applied to the document. A normal page has a matte finish. Glossy finish can be requested to be applied to the page as it’s printed. The finish is distinct from the type of media. Therefore, a matte finish can be requested for glossy media, and a glossy finish can be requested for plain or matte paper.

?&b#F

# = 0 - Matte finish

1 - Glossy finish

Default =0

Range = 0, 1 (command is ignored for invalid values)

The finish mode must be set before the first page is marked and applies to all the pages in the document. Each document defaults to a matte finish.

4-6 Modifying Output Color EN

The PCL Print Model

Introduction

The Print Model feature allows images and characters to be filled with color, with any of the printer's predefined shading or cross-hatch patterns, or with a user-defined pattern. Images include any raster graphic, such as one created with PCL raster graphics commands (as described in Chapter 6, Raster Graphics); a rectangular fill area (as described later in this chapter as PCL Rectangular Area Fill Graphics); or characters selected from any font.

Figure 5-1 illustrates the use of the print model. The following definitions are helpful in describing Print Model operation:

Figure 5-1 Print Model Imaging

EN The PCL Print Model 5-1

• Pattern—The design which is “painted” through the non-white area of the source image onto the destination image. The pattern is defined by the Current Pattern ( may be a color pattern or a single-plane monochrome mask, such as the printer's internal predefined shading or cross-hatch patterns, or a user-defined pattern. Foreground color is not applied to a user-defined color pattern.

When printing a page, text and raster images are printed using the current pattern. Once the current pattern is specified, it stays in e f fect until an ot her is selected or t he pri n ter is re se t. A reset returns the current pattern to its default value (100% black). The current pattern does not always apply to rectangular area fill, which uses patterns defined by the rectangular area fill pattern commands.

• Foreground Color—Foreground color is selected from the current palette using the Foreground Color command (

?*v#S). Foreground color affects everything except

user-defined color patterns and HP-GL/2 primitives. Raster color mixes with foreground color (see Chapter 6 “Color Raster Graphics”).

• Texture—Texture is another name for the combination of pattern and foreground color, or for a color pattern which is not combined with a foreground color.

• Source Image—the Source Image is an image in which the non-white bits are replaced by the specified pattern. The source image functions like a stencil through which the pattern is applied to the destination image. The source image may be one of the following: HP-GL/2 primitives, rules, characters, or raster images (single plane mask or multi-plane color)

• Destination Image—The image onto which the source image/texture combination is placed. The destination image includes any images placed through previous operations.

• Source Transparency Mode—The transparency or opaqueness of the source image’s “white” pixels as they are applied to the destination image (see the note below). Setting the source transparency mode to 1 (opaque) applies the source image's white pixels to the destination image; with a setting of 0 (transparent), these pixels have no effect on the destination.

?*v#T) command. It

5-2 The PCL Print Model EN

• Pattern Transparency Mode—The transparency or opaqueness of the “white pixels” in the pattern (see the note below). When set to 0 (transparent), these pixels have no effect on the destination; when set to 1 (opaque), they are applied through the black pixels of the source pattern to the destination.

• Logical Operations—the Print Model uses logical operations, such as AND, OR, XOR, and NOT when determining which bits of the source, pattern, and texture become part of the resulting image. The Logical Operations command ( can vary the logical operation used, thus varying the outcome.

Note For RGB color images, “white” pixels are those for which all color

primaries are 255. For CMY color images, “white” pixels are those for which all color primaries are 0.

For all rendering algorithms, white dots introduced in the dithering process are not subject to transparency modes.

Figure 5-2 illustrates the effects of the source and pattern transparency modes on the final image. (The transparency modes work a little differently with rectangular area fill—see “Pattern Transparency for Rectangular Area Fill” near the end of this chapter.)

?*l#O)

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

Figure 5-2 Opaque and Transparency Modes

EN The PCL Print Model 5-3

Figure 5-3 demonstrates the transparency modes. In the first example (1a), the transparency mode for both the source image and the pattern is transparent. Since the source mode is “transparent,” only the non-white region (the circle) of the source image is overlaid on the destination. Since the pattern mode is also transparent, the patterned source image is applied only to the white areas of the destination.

In the second example (1b), the source mode is still “transparent,” b ut the pattern mode is “opaque” – so the pattern's white pixels are applied to the destination. The resulting image shows the entire circle region visible and patterned.

In the third example (1c), the source mode is “opaque” and the pattern mode is transparent. Since the source mode is opaque, the entire source image (the circle and the surrounding square) appears overlaid onto the destination. The pattern, however , is allowed to pour through only onto the white-pixeled area of the destination. The circle 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 entire source image is overlaid onto the destination, and the entire circle is patterned.

5-4 The PCL Print Model EN

Figure 5-3 Effect of Transparency Modes on Images

EN The PCL Print Model 5-5

Command Sequence

The table below shows the Print Model command sequence for selecting a current pattern and using it to fill a destination image. The commands for specifying transparency modes, logical operations, and patterns are discussed beginning on the following page. Foreground color is described in Chapter 3.

Operation Comments

Download Page Data Prior raster and character data

downloaded to the page is considered destination image.

Select Transparency Modes

Specify the Logical Operation If a logical operation other than the default

Select Specific Pattern ID Pattern ID

Download User-Defined Pattern If using a user-defined pattern, it must be

Select Pattern

Specify the Foreground Color For color printers, specify a Foreground

Download Source Image Data Raster image/characters

Return to regular print mode Default current pattern and transparency

Download remaining page data Transfer data for regular printing, or the

End of Page Data

?*v#N (source) and/or ?*v#O (pattern)

(TSo-252) is desired, specify the operation with the

?*l#O command.

?*c#G

downloaded to the printer before using it.

?*v4T (selects downloaded pattern)

Color (

?*v#S) if des ired. (This step is

unnecessary if a color pattern is used.)

modes: selected) and (transparency modes selected).

above process may be repeated to produce another print model effect.

?*v0T (100% black pattern

?*v0N ?*v0O

5-6 The PCL Print Model EN

Source Transparency Mode Command

The Select Source Transparency Mode command sets the source image's transparency mode to transparent or opaque. This command determines whether the source's white pixels are applied to the destination.

? * v # N

# = 0 - Transparent

1 - Opaque

Default =0

Range = 0, 1 (other values cause the command to be ignored)

With a transparency mode of “0” (transparent), the white regions of the source image are not copied onto the destination. With a transparency mode of “1” (opaque), the white pixels in the source are applied directly onto the destination. White pixels are unaffected by pattern or foreground color; they are either white or transparent.

Note For RGB color images, “white” pixels are those for which all color

primaries are 255. For CMY color images, “white” pixels are those for which all color primaries are 0.

White dots introduced in the dithering process are not subject to transparency modes.

Refer to the preceding definitions and the discussion of Figure 5-3 for an explanation of the effects of source transparency.

EN The PCL Print Model 5-7

Pattern Transparency Mode Command

The Pattern Transparency Mode command sets the pattern's transparency mode to transparent or opaque.

? * v # O

# = 0 - Transparent

1 - Opaque

Default =0

Range = 0, 1 (other values cause the command to be ignored)

A transparency mode of “0” (transparent) means that the white regions of the pattern image are not copied onto the destination. A transparency mode of “1” (opaque) means that the white pixels in the pattern are applied directly onto the destination.

Note When printing white rules, the pattern transparency is treated as if it

were “opaque”; white rules erase black rules regardless of the transparency mode.

For RGB color images, “white” pixels are those for which all color primaries are 255. For CMY color images, “white” pixels are those for which all color primaries are 0.

White dots introduced in the dithering process are not subject to transparency modes.

Refer to the preceding definitions and the discussion of Figure 5-2 and Figure 5-3 for an explanation of the effects of pattern transparency.

5-8 The PCL Print Model EN

Logical Operations

The basic print model defines how a pattern, source image, and destination image are applied to each other using the print model’s transparent and opaque modes to produce a resulting image. The Logical Operations ( operation is to be performed on the source, texture, and destination to produce a new destination. Transparency modes should be specified before the logical operation is performed or printable data is sent.

The print model process consists of the following steps:

1 Specify source and/or pattern transparency modes, if desired. 2 Specify the logical operation (or use the default). 3 Define the desired operands (source, destination, pattern).

Definitions

Source: The source image may be one of the following:

• HP-GL/2 primitives

• Rules

• Characters

• Raster images (single plane mask or multiplane color)

Destination: The destination image contains whatever is currently defined on the page. It includes any images placed through previous operations.

?*l#O) command specifies which logical

Pattern or Texture: The pattern is defined by the Select Current Pattern command ( interchangeably in this section.

Transparency Modes: The white pixels of the source and/or pattern may be made transparent (source transparency 0, pattern transparency 0). The destination shows through these areas. Transparency modes are set by the Source Transparency ( and Pattern Transparency (

The Print Model allows logical operations, such as AND, OR, XOR, NOT, to be performed on source, texture, and destination images. Transparency modes and Logical Operation must be specified before printable data is sent.

EN The PCL Print Model 5-9

?*v#T). The terms pattern and texture are used

?*v#N)

?*v#O) commands.

Operators

• Source Transparency (specified before logical operation; default is transparent)

• Pattern Transparency (specified before logical operation; default is transparent)

• Logical Operators (default is Texture OR Source)

Operands

• Source objects: character cell, raster image, rule, HP-GL/2 vectors and polygons

• Texture: foreground color + pattern mask, color pattern (format 1 ).

• Destination: current page definition

Operation

• IF (source transparent && source == white) RETUR N destination

• IF (pattern transparent && pattern == white && source != white) RETURN destination

• ELSE RETURN (logical op (source, texture, destination)

5-10 The PCL Print Model EN

Assuming three bits per pixel, the following diagram shows the process.

Figure 5-4 Logical Operations and the Print Model

Note The Logical Operation command (?*l#O) provides 255 possible

logical operations. All of these logic operations map directly to their ROP3 (raster operation) counterparts (see the Microsoft Document, Reference, Volume 2, Chapter 11, Binary and Ternary Raster Operation Codes).

The logical operations were defined for Microsoft Windows for an RGB color space. In RGB space, a “1”' is white and a “0” is black.

EN The PCL Print Model 5-11

Logical Operations and Transparency Interactions

As described above, transparency modes operate in addition to logical operations. The Logical Operations (ROP3) in Table 5-4 are true only if source and pattern transparency (for white pixels) are explicitly set to opaque ( transparency modes are transparent (defaulted), the additional operations shown below must be performed to achieve the final result.

The four basic interactions are:

• Case 1: Source and Pattern are opaque. Texture = Color & Pattern. RETURN ROP3 ( Dest, Src, Texture ).

• Case 2: Source is opaque, Pattern is transparent. Texture = Color & Pattern. Temporary_ROP3 = ROP3 ( Dest, Src, Texture ). Image_A = Temporary_ROP3, & Not Src. Image_B = Temporary_ROP3 & Pattern. Image_C = Not Pattern & Src & Dest. RETURN Image_A | Image_B | Image_C

• Case 3: Source is transparent, Pattern is opaque. Texture = Color & Pattern. Temporary_ROP3 = ROP3 ( Dest, Src, Texture ). Image_A = Temporary_ROP3 & Src. Image_B = Dest & Not Src. RETURN Image_A | Image_B

• Case 4: Source and Pattern are transparent Texture = Color & Pattern. Temporary_ROP3 = ROP3 ( Dest, Src, Texture ). Image_A = Temporary_ROP3 & Src & Pattern. Image_B = Dest & Not Src. Image_C = Dest & Not Pattern. RETURN Image_A | Image_B | Image_C.

?*v1N and ?*v1O). If source and/or pattern

Note The Transparency Mode is applied based on the color of each pixel.

However , the Logical Operation is applied on a bit-by-bit basis without regard to color. In order to obtain a result consistent with the Logical Operation, the transparency modes should be set to Source Opaque and Pattern Opaque. In order to obtain a result consistent with the desired transparency mode, the Logical Operation should be set to 252 and the foreground color set to black.

5-12 The PCL Print Model EN

Logical Operation Command

Specifies the logical operation (ROP) to be performed in RGB color space on destination, source and texture to produce new destination data. Texture is defined as a combination of pattern and foreground color.

?*l # O

# = Logical operation value (see Table 5-4)

Default = 252 (TSo)

Range = 0 to 255

The Logical Operation code, or Raster OPeration (ROP) code, is simply a systematic method of encoding all of the 256 possible ways that a Texture, Source, and Destination can be combined. Table 5-4 gives a table of ROPs from ROP 0 to R OP 255, where each operation is defined as a logic equation. This table can be difficult to understand and use. Furthermore, it does not show the differences that depend on the color space. A truth table is an alternative method for understanding the results of a logical operation. When used with ROPs for finding the resulting destination value, it is more easily understood than the logic operation.

ROP

252 (11111100)

RGB

(T)exture (S)ource (D)estination (D)estination

11 1 1 11 0 1 10 1 1 10 0 1 01 1 1 01 0 1 00 1 0 00 0 0

The first destination column is ignored and the second destination column is the result of the ROP (White = [1,1,1] and Black = [0,0,0] ).

EN The PCL Print Model 5-13

For example, the logic equation for ROP 252 in the RGB color space is T OR S, which is shown as TSo in Table 5-4. The truth table for the ROP is shown above, and can be seen to correspond to the logic equation TSo, that is, D gets the value of T OR S without regard to the current value of D. Furthermore, the binary value of 252 is 11111100 and corresponds with the value of the D for all the combinations of T and S, when the truth table starts with (1, 1, 1) and ends with (0, 0, 0).

It’s possible to derive the logical operation for a truth table and to create a truth table for a logical operation. However, the most important point is that the binary value of the ROPs number gives the Destination for all possible combinations of Texture, Source, and Destination.

The way the bits of the ROPs number map to the combinations of T e xture, Source, and Destination depends on whether the color space is RGB or CMY . The least significant bit of the RGB ROP value maps to (0, 0, 0), the color black in RGB, and the most significant bit to (1, 1, 1), white in RGB. On the other hand, the CMY ROP reverses the mapping. This reversal hinges on the fact that RGB and CMY are the inverse of each other, i.e., RGB Black is (0, 0, 0) and CMY Black is (1, 1, 1), white. All other colors show the same relationship.

ROPs in the RGB Color Space

The RGB ROP truth tables shown in Tabl e 5-1 illustrate how ROP 252 and ROP 90 work, and most importantly how the bits in the ROP map show destination values for each combination of Texture, Source and Destination. A “1” in the RGB color space represents white and a “0” black, which makes determining what shows on paper cumbersome for users since the paper is marked when the Destination has a “0” value.

5-14 The PCL Print Model EN

Table 5-1. RGB ROP Truth Tables

ROP

(11111100) (01011010) n=(b

252 ROP

rgb

90 ROP

rgb

7b6b5b4b3b2b1b0

TSDD TSDD TSDROP n D

1111

white

1110

white

111b7b 1101 1101 110b6b 1011 1010 101b5b 1001 1001 100b4b 0111 0111 011b3b 0101 0100 010b2b 0010 0011 001b1b 0000

black

0000

black

000b0b

ROPs in the CMY Color Space

The CMY ROP truth tables in Table 5-2 shows examples of how the ROPs number determines the value of the Destination for all combinations of Texture, Source, and Destination. In the CMY color space a “0” is the absence of ink (white) and a “1” is the presence of ink (black), the opposite of the RGB color space value for black and white. Therefore, the ROPs results (Destination values) for the CMY color space are the opposite (negation) of the RGB values. However, a CMY ROP is easier to use when determining if the page is marked, since a “1” denotes marking.

)

7 6 5 4 3 2 1 0

EN The PCL Print Model 5-15

Table 5-2. CMY ROP Truth Tables

ROP

(00000011) (10100101) n=(b

252 ROP

cmy

90 ROP

cmy

7b6b5b4b3b2b1b0

TSDD TSDD TSDROP n D

0000

white

0001 0010 0010 001b 0100 0101 010b 0110 0110 011b 1000 1000 100b 1010 1011 101b 1101 1100 110b 1111

black

1111

white

000b7!b7

black

111b0!b0

6 5 4 3 2 1

Using a ROP

The first step in using a ROP is to determine which color space you're in: RGB or CMY. Then determine the binary value of the ROP used. For example, suppose you want to use ROP 90 in the CMY color space. The binary equivalent of 90 is 01011010 when written in most significant to least significant bit order.

)

!b6 !b5 !b4 !b3 !b2 !b1

Looking at the truth table for ROP 90 in Table 5-2 you can see that the only time the page is marked is when the Texture and Destination are both “0” or both “1.” However, the same result is given by negating each bit of the ROP number, 90, to give 10100101. Using the general table for CMY ROPs (the rightmost table in Table 5-2) you can plug the bit values from 90 into b

through b0 to obtain the values in the

truth table for ROP 90. Similarly, using ROP 90 in the RGB color space entails plugging 01011010 in the general table for RGB ROPS (the rightmost table in Table 5-1) to obtain the values in the truth table for ROP

90 (also in Table 5-1). This process works for any value

rgb

from 0 to 255 and can be used to determine what will show for any given ROP, in either the RGB or CMY color spaces.

5-16 The PCL Print Model EN

Note Since PCL logical operations are interpreted in RGB space

(white = 1, black = 0) rather than in CMY space (white = 0, black = 1), the results may not be intuitive. For example, ORing a white object with a black object in RGB space yields a white object. This is the same as ANDing the two objects in CMY space. It must be remembered that the printer operates in CMY space and inverts the bits. To convert from one color space to the other, write the ROP in binary format, invert the bits, and reverse the order.

When source and/or pattern transparency modes are set opaque (not defaulted), values specified by this command map directly to the ROP3 (raster operation) table values on the following page. However, when source and/or pattern transparency modes are set transparent, the additional operations shown on the previous page must be performed to achieve the final result.

Logical operations in the table are shown in RPN (reverse polish notation). For example, the value 225 corresponds to TDSoxn, the logical function of:

NOT (texture XOR (destination OR source))

Note ?*l # O is the PCL Version of the HP-GL/2 MC command.

This command sets the ROP value which affects not only PCL operation but also the HP-GL/2 ROP value.

EXAMPLE

The Logical Operation default value is 252 (TSo), corresponding to a logical function of:

(texture | source)

EN The PCL Print Model 5-17

The result is computed below (source and pattern opaque).

Table 5-3. Logical Operation (ROP3)

Bits

7 6 5 4 3 2 1 0

Texture 1 1 1 1 0 0 0 0 Source 1 1 0 0 1 1 0 0 Destination 1 0 1 0 1 0 1 0 ROP3 (source & pattern) 11111100

(decimal 252)

Each column of destination, source, and texture values are the input to the logical function. The result, 252, is the value that would be sent to identify the logical operation (refer to page 5-12 for source/pattern transparency interactions ).

Table of Logical Operations

The Logical Operations (ROP3) table (Table 5-4) shows the mapping between input values and their logical operations. Note that the logical operations are specifi ed as RPN (reverse polish notation ) equations. Here is a key to describe what the Boolean Function values mean;

S = Source a = AND T = Texture o = OR D = Destination n = NOT

x = EXCLUSIVE OR

Note Since logical operations are interpreted in RGB space (white = 1 and

black = 0) rather than in CMY space (white = 0 and black = 1), the results may not be intuitive. For e xample, ORing a white object with a black object in RGB space yields a white object. This is the same as ANDing the two objects in CMY space. It must be remembered that the printer operates in something similar to a CMY space and inverts the bits and reverses the order.

5-18 The PCL Print Model EN

Table 5-4. Logical Operations (ROP3)

Input Value

Boolean

Function Input Value

Boolean

Function

0 0 27 SDTSxaxn 1 DTSoon 28 TSDTaox 2 DTSona 29 DSTDxaxn 3 TSon 30 TDSox 4 SDTona 31 TDSoan 5DTon32DTSnaa 6 TDSxnon 33 SDTxon 7 TDSaon 34 DSna 8 SDTnaa 35 STDnaon

9 TDSxon 36 STxDSxa 10 DTna 37 TDSTanaxn 11 TSDnaon 38 SDTSaox 12 STna 39 SDTSxnox 13 TDSnaon 40 DTSxa 14 TDSonon 41 TSDTSaoxxn 15 Tn 42 DTSana 16 TDSona 43 SSTxTDxaxn 17 DSon 44 STDSoax 18 SDTxnon 45 TSDnox 19 SDTaon 46 TSDTxox 20 DTSxnon 47 TSDnoan 21 DTSaon 48 TSna 22 TSDTSanaxx 49 SDTnaon 23 SSTxDSxaxn 50 SDTSoox 24 STxTDxa 51 Sn 25 SDTSanaxn 52 STDSaox 26 TDSTaox 53 S TDSxnox

EN The PCL Print Model 5-19

Table 5-4. Logical Operations (ROP3) (continued)

Boolean

Input Value

54 SDTox 81 DSTnaon 55 SDToan 82 DTSDaox 56 TSDToax 83 STDSxaxn 57 STDnox 84 DTSonon 58 STDSxox 85 Dn 59 STDnoan 86 DTSox 60 TSx 87 DTSoan 61 STDSonox 88 TDSToax 62 STDSnaox 89 DTSnox 63 TSan 90 DTx 64 TSDnaa 91 DTSDonox 65 DTSxon 92 DTSDxox 66 SDxTDxa 93 DTSnoan 67 STDSanaxn 94 DTSDnaox 68 SDna 95 DTan

Function Input Value

Boolean

Function

69 DTSnaon 96 TDSxa 70 DSTDaox 97 DSTDSaoxxn 71 TSDTxaxn 98 DSTDoax 72 SDTxa 99 SDTnox 73 TDSTDaoxxn 100 SDTSoax 74 DTSDoax 101 DSTnox 75 TDSnox 102 DSx 76 SDTana 103 SDTSonox 77 SSTxDSxoxn 104 DSTDSonoxxn 78 TDSTxox 105 TDSxxn 79 TDSnoan 106 DTSax 80 TDna 107 TSDTSoaxxn

5-20 The PCL Print Model EN

Table 5-4. Logical Operations (ROP3) (continued)

Input Value

Boolean

Function Input Value

Boolean

Function

108 SDTax 135 TDSaxn 109 TDSTDoaxxn 136 DSa 110 SDTSnoax 137 SDTSnaoxn 111 TDSxnan 138 DSTnoa 112 TDSana 139 DSTDxoxn 113 SSDxTDxaxn 140 SDTnoa 114 SDTSxox 141 SDTSxoxn 115 SDTnoan 142 SSDxTDxax 116 DSTDxox 143 TDSanan 117 DSTnoan 144 TDSxna 118 SDTSnaox 145 SDTSnoaxn 119 DSan 146 DTSDToaxx 120 TDSax 147 STDaxn 121 DSTDSoaxxn 148 TSDTSoaxx 122 DTSDnoax 149 DTSaxn 123 SDTxnan 150 DTSxx 124 STDSnoax 151 TSDTSonoxx 125 DTSxnan 152 SDTSonoxn 126 STxDSxo 153 DSxn 127 DTSaan 154 DTSnax 128 DTSaa 155 SDTSoaxn 129STxDSxon156 STDnax 130DTSxna157DSTDoaxn 131 STDSnoaxn 158 DSTDSaoxx 132SDTxna159TDSxan 133 TDSTnoaxn 160 DTa 134 DSTDSoaxx 161 TDSTnaoxn

EN The PCL Print Model 5-21

Table 5-4. Logical Operations (ROP3) (continued)

Boolean

Input Value

162 DTSnoa 189 SDxTDxan 163 DTSDxoxn 190 DTSxo 164 TDSTonoxn 191 DTSano 165TDxn192 TSa 166 DSTnax 193 STDSnaoxn 167 TDSToaxn 194 STDSonoxn 168 DTSoa 195 TSxn 169DTSoxn196STDnoa 170 D 197 STDSxoxn 171 DTSono 198 SDTnax 172 STDSxax 199 TSDToaxn 173DTSDaoxn200 SDToa 174 DSTnao 201 STDoxn 175DTno202DTSDxax 176 TDSnoa 203 STDSaoxn

Function Input Value

Boolean

Function

177TDSTxoxn204 S 178 SSTxDSxox 205 SDTono 179 SDTanan 206 SDTnao 180 TSDnax 207 STno 181 DTSDoaxn 208 TSDnoa 182 DTSDTaoxx 209 TSDTxoxn 183SDTxan210TDSnax 184 TSDTxax 211 STDSoaxn 185DSTDaoxn212SSTxTDxax 186 DTSnao 213 DTSanan 187DSno214TSDTSaoxx 188 STDSanax 215 DTSxan

5-22 The PCL Print Model EN

Table 5-4. Logical Operations (ROP3) (continued)

Input Value

Boolean

Function Input Value

Boolean

Function

216 TDSTxax 236 SDTao 217 SDTSaoxn 237 SDTxno 218 DTSDanax 238 DSo 219STxDSxan239 SDTnoo 220 STDnao 240 T 221SDno241TDSono 222 SDTxo 242 TDSnao 223 SDTano 243 TSno 224 TDSoa 244 TSDnao 225TDSoxn245 TDno 226 DSTDxax 246 TDSxo 227TSDTaoxn247 TDSano 228 SDTSxax 248 TDSao 229TDSTaoxn249 TDSxno 230 SDTSanax 250 DTo 231 STxTDxan 251 DTSnoo 232 SSTxDSxax 252 TSo 233 DSTDSanaxxn 253 TSDnoo 234 DTSao 254 DTSoo 235DTSxno255 1

EN The PCL Print Model 5-23

Pixel Placement

HP PCL 5 printers place pixels at the intersection of the squares of a theoretical, device-dependent grid covering the printable area on the page. Depending on the image and the logical operation in effect, a problem may occur when the sides of two polygons touch each other—the pixels along the common border may be printed twice or not at all. For example, a source rectangle consisting of all 1’s that is XORed with a destination consisting of all 1’s produces a white rectangle; but if another source rectangle is placed on the page touching the first rectangle, the two rectangles will be white-filled except at their common border ( (1^1) ^ 1 = 1).

To correct situations where this problem occurs, the PCL printer language provides a choice of pixel placement models: grid intersection and grid centered. The grid intersection model is the default: pixels are rendered on the intersections of the device-dependent grid covering the page. In the grid-centered model, the number of rows and columns are each reduced by one, and pixels are placed in the center of the squares, rather than at the intersections.

The following example illustrates the concepts of the two models (see Figure 5-5). Assume a rectangle extends from coordinate position (1,1) to position (3,4). As shown below, for the same coordinates, the grid-centered model produces a rectangle that is one dot row thinner and one dot row shorter than the grid intersection model. Thus, the grid-centered model should be selected when two or more polygons on a page may share a common border.

Since PCL printers print only at the intersections of the grid, the actual implementation of the grid-centered model is shown on the right.

5-24 The PCL Print Model EN

Figure 5-5 Pixel Placement

Note The grid-centered method is used by Microsoft Windows.

When rectangular area fills are used and grid intersection is used, an overlapping of pixels can occur if rectangular area fills are placed adjacent to one another (as shown below). Depending on the raster operation presently in effect, this overlap can produce undesirable results in the final printed image. To avoid this problem, use the grid-centered method.

EN The PCL Print Model 5-25

Note Since PCL printers print only at intersections, grid- centered pixel

placement is implemented as shown on the right.

Figure 5-6 Pixel Placement Variations

There are two commands that modify the pixel placement function: the PCL Pixel Placement command ( Placement command (PP).

5-26 The PCL Print Model EN

?*l#R) and the HP-GL/2 Pixel

Pixel Placement Command

Determines how pixels are rendered in images.

?*l # R

# = 0 - Grid intersection

1 - Grid centered

Default =0

Range = 0, 1 (command is ignored for other values)

Two models are used for rendering pixels when an image is placed on paper:

• Grid Intersection Mode l

• Grid Centered Model

This command can be used multiple times per page. It has no effect except to switch the model being used for imaging.

Note The PCL Pixel Placement command determines how pixels are

placed for both PCL and HP-GL/2 operation. This command performs the same function as the HP-GL/2 PP

command described in Chapter 7.

EN The PCL Print Model 5-27

Filling with Patterns

The procedure for applying patterns to text, raster images, and rectangular areas is essentially the same, except that for text and raster images the Current Pattern ( rectangular areas the Fill Rectangular Area ( used. The procedures below describe how to fill with PCL and HP-GL/2 patterns.

Patterns for Text and Raster Images

Use the following general procedure to fill text and raster images with a non-solid pattern.

?*v#T) command is used, and for

?*c#P) command is

1 Specify the Pattern ID (

patterns, select an ID that specifies the desired pattern.

2 Download the pattern (

patterns only. The downloaded pattern adopts the current pattern ID.

3 Apply the pattern to all subsequent text and raster images.

Specify the current pattern type (

?*c#G) command. For HP-defined

?*c#W). This step is for user-defined

?*v#T).

Patterns for Rectangles

Use the following general procedure to apply a non-solid pattern to rectangular areas.

1 Specify the Pattern ID (

an ID that matches an HP-defined pattern.

2 Download the pattern (

patterns only. The downloaded pattern adopts the current pattern ID.

3 Define the rectangle. Position the cursor and specify the

rectangle size (

4 Apply the pattern to the rectangle. Send the Fill Rectangular Area

command (

?*c#A, ?*c#B or ?*c#H, ?*c#V).

?*c#P).

?*c#G). For HP-defined patterns, select

?*c#W). This step is for user-defined

HP-GL/2 Patterns

PCL patterns can be used in HP-GL/2 mode, but HP-GL/2 patterns cannot be used in PCL mode. Using HP-GL/2, patterns are downloaded using the RF (Raster Fill) command, and applied using the FT (Fill Type) or SV (Screened Vectors) commands.

5-28 The PCL Print Model EN

Pattern ID (Area Fill ID) Command

The Pattern ID command (formerly called Area Fill ID) identifies the specific shading, cross -h atc h, or user -defi ned pattern. (This command is also used for rectangular area fill, described later in this chapter.)

? * c # G

Selecting Shaded patterns: Selecting Cross-Hatch

# = 1 thru 2 = 1- 2% shade # = 1 - Pattern #1

3 thru 10 = 3-10% shade 2 - Pattern #2 11 thru 20 = 11-20% shade 3 - Pattern #3 21 thru 35 = 21-35% shade 4 - Pattern #4 36 thru 55 = 36-55% shade 5 - Pattern #5 56 thru 80 = 56-80% shade 6 - Pattern #6 81 thru 99 = 81-99% shade 100 = 100% shade

Selecting User-Defined patterns:

# = ID number of user-defined pattern

Not supported on all PCL 5 printers. Refer to the “PCL Feature Support Matr ix” in

Chapter 1 of the PCL 5 Comparison Guide for specifics.

patterns:

Default = 0 (no pattern)

Range = 0 – 32767 (values outside the range are ignored)

For rectangular areas, the pattern “material” is determined by both the pattern ID and the value of the Fill Rectangular Area command. For other images, the pattern material is determined by the pattern ID and the value of the Select Pattern command.

Figure 5-7 and Figure 5-8 illustrate the HP-defined shading patterns and cross-hatched patterns, respectively.

Note This command is used for both the Select Pattern and Rectangular

Area Fill graphics. For user-defined patterns, this command, sent prior to downloading a

user-defined pattern, assigns an ID pattern number to the downloaded pattern. (For more information, see “User-Defined Pattern Graphics,” later in this chapter.)

EN The PCL Print Model 5-29

Figure 5-7 Shading Patterns

5-30 The PCL Print Model EN

Figure 5-8 Cross-Hatch Patterns

EN The PCL Print Model 5-31

Select Current Pattern Command

The Select Current Pattern command identifies the type of pattern to be applied onto the destination.

? * v # T

# = 0 - Solid black or foreground color

1 - Solid white 2 - Shading pattern 3 - Cro ss- hatch patte rn 4 - User-defined pattern

Default =0

Range = 0 - 4 (values outside of range are ignored)

This command selects which type of pattern is applied. For values 2, 3, and 4, the desired shading level, cross-hatch pattern, or user-defined pattern number is identified by the Pattern ID command described earlier in this chapter.

Note For selecting or changing the current pattern, the Select Current

Pattern ( together. Sending the current pattern (Select Current Pattern command) alone does not change the current pattern; the P attern ID must be sent first. However, when selecting solid white (white rule) or solid black (black rule), only the Select Current Pattern command is required.

?*v#T) and the Pattern ID (?*c#G) commands work

Once a current pattern is selected, that pattern applies to all images placed on the page until a new pattern is selected.

5-32 The PCL Print Model EN

User-Defined Pattern Graphics

In addition to the eight shading patterns and six cross-hatch patterns, users can design their own fill patterns. These user-defined patterns are downloaded to the printer and controlled using three commands:

• Download Pattern

• Set Pattern Reference Point

• Pattern Control

?*c#W [data]

?*p#R

?*p#Q

Using User-Defined Patterns

To create a new pattern, a user defines a binary raster data image as a base pattern. This base pattern is downloaded to the printer using the User-Defined Pattern command. Prior to downloading the pattern, a Pattern ID command is sent to assign the user pattern an ID number. This ID number is used to select the pattern for printing and for pattern management.

To apply the pattern to an image, the printer duplicates or tiles (like placing ceramic tiles) the pattern across and down the page. This pattern can be applied to any image, including rectangular area fill.

Figure 5-9 User-Defined Base Pattern Example

A user-defined pattern may be applied to any image in the same manner as the internal cross-hatch or shade patterns.

EN The PCL Print Model 5-33

Note For efficient memory usage and improved performance, it is strongly

recommended that user-defined patterns should be 8x8, 16x16, or 32x32 in size. Specification of patterns that are either 1 pixel in height or width is strongly discouraged.

If user-defined halftones are also used, they need to be either the same size or multiples of each other to avoid render anomalies due to each pattern being rendered differently across the page (if tiled), or due to variations in xy position.

How the Printer Tiles a Pattern

A user-defined base pattern is a rectangular binary pattern stored in the printer. To apply the pattern to an image area on the page, the printer duplicates the base pattern across and down the page. This process is referred to as tiling. (The pattern is only applied to those areas on the page for which the pattern is required.)

5-34 The PCL Print Model EN

Figure 5-10 Pattern Layout Across the Printable Area

EN The PCL Print Model 5-35

Pattern Reference Point

The pattern reference point is a position on the logical page at which the base pattern is positioned for tiling. The upper left corner of the base pattern is positioned at this point (see Figure 5-10). The default pattern reference point is position 0,0. However, it is possible to set the pattern reference point to the current cursor position. This allows the pattern to be positioned or adjusted for fill areas. The pattern reference point may be shifted more than once for as many fill areas as there are on a page (the area must be filled before the tile point is moved for the next fill area).

Figure 5-11 shows two areas filled with the pattern reference point fixed at the default (0,0) position. The lower portion of the illustration shows two areas in which the pattern reference point was moved to the upper left corner of each area and the area filled separately.

5-36 The PCL Print Model EN

HP (Hewlett-Packard) PCL User Manual

Specifications and Main Features

Frequently Asked Questions

User Manual

PCL 5 Color Technical Reference Manual

Inside This Manual

Manual Organization

Related Documents

Contents

Introduction

Working with color documents

PCL 5 Color Concepts

Color

Color Specifications and Color Spaces

Color Management and the Standard Red, Green, Blue Color Space

Palettes and Color Selection

PCL 5 Color Graphics Context

PCL 5 Color Mode

PCL 5 Raster Images

Pixels and Pixel Encoding

Well-Behaved Raster

Using Color Modes

Introduction

Simple Color Mode

PCL Imaging Mode

Configure Image Data (CID) Command

HP-GL/2 Imaging Mode

Using Palettes

Introduction

Saving the Palette

Push/Pop Palette Command

Palette Management by ID

Select Palette Command

Palette Control ID

Palette Control

Simple Color Palettes

CID Color Palettes

Device RGB and sRGB Palettes

Device CMY Palettes

HP-GL/2 Palettes

Foreground Color

Foreground Color Command

Programming Color Palettes

Modifying Output Color

Introduction

Halftone Render Algorithms

Render Algorithm Command

Monochrome Printing

Monochrome Print Mode Command

Driver Configuration Command

Finish Mode Command

The PCL Print Model

Introduction

Command Sequence

Source Transparency Mode Command

Pattern Transparency Mode Command

Logical Operations

Logical Operations and Transparency Interactions

Logical Operation Command

ROPs in the RGB Color Space

ROPs in the CMY Color Space

Using a ROP

Table of Logical Operations

Pixel Placement

Pixel Placement Command

Filling with Patterns

Pattern ID (Area Fill ID) Command

Select Current Pattern Command

User-Defined Pattern Graphics

Using User-Defined Patterns

How the Printer Tiles a Pattern

Pattern Reference Point