6 . 3 . 3 Printing Color Models

Several color models have evolved for use in printing. Printing in color is the act of putting inks on paper. This action reverses the additive nature of color produced with light into a subtractive process. A red, green, and blue light source will appear white when combined. Red, green, and blue inks on paper will create a black area.

CMYK

The printing industry and many color computer printers use the CMYK (Cyan Magenta Yellow blacK) color model to create fullcolor printed images. This model is also know as process color. Four inks with the colors cyan, magenta, yellow, and black are combined using halftoning techniques to create the illusion of continuoustone color images. (See_ Section 6. 2 Dots and Pictures in Chapter 6 Media and Document Integration for a discussion of halftoning.) The perceived subtle nature of color created by the small dots of CMYK colors are a side effect of our perception. Take a look at a color magazine photo with a magnifying glass. The color of a person's skin is not really there! The color mixing is in our brains.

SPOT COLOR

Spot color printing refers to the use of one, two, three, or more single distinct colors within the document. Common uses are to color all section headings a unique color or to

color arrows that point out information.(8)

You must use a color system to specify a color and hope that what is actually printed represents what you specified. The most common system is the Pantone Color Matching system. Some of the more complete electronic publishing systems provide software support for the use of particular spot color systems.

WYSIWIP, or What You Select Is What Is Printed, can become problematic in the case of spot color. Color matching systems, as these things are known, exist as swatch books from which you select a color. These expensive books contain all the colors for a particular color system; for example, PANTONE or COLORCURVE. Note that the names of the various spot color systems are not generic color terms; instead, they are registered trademarks of their respective holders. The inks used to print these swatch books are specially mixed solid colors. If a print job uses a single spot color and the printer indeed uses the special ink, everything should be fine. If, however, the spot color will be produced using process (CMYK) colors, you may be in for a surprise. The use of CMYK process colors will be only a simulation of the selected swatch color. The Trumatch Swatching System is an exception to this rule and is based on CMYK process color. Its swatch book is indeed printed with process colors.(9)

Cost is another significant issue with color printing. For example, if you intend to produce color PostScript files, you typically must give the printer one file for each spot color. This can quickly raise your production costs. However, spot color is less expensive than fullprocess color printing. In fact, spot color printing is a costeffective means of using color. Typically, "you can expect to pay 25-35 percent above the cost of a one-color page for each additional press color."(10) However, only your printer knows for sure.

PANTONE SYSTEM

The Pantone Matching System is a widely used color specification system. The actual colors are a set of more than 533 colors, each with a name or number. You can purchase sample books with the colors printed on coated or uncoated stock. The color of an ink appears more saturated on coated stock because the coating prevents the ink from getting into the fabric of the paper.

The Pantone system is widely used largely because of the variety of swatch books available. These include small books, books with tearout chips, twocolor comparisons, tint selectors, and process color simulations, all on coated or uncoated stock.

Although the Pantone Matching System originated for the printing industry, it is also widely used in the computerbased, graphic arts industry. Programs such as FrameMaker and Adobe Illustrator allow you to select Pantone colors. These can produce reasonable

facsimiles of the printed output right on the display screen. However, as discussed in the earlier section on Color Models, the display screen will not be an accurate rendition of the printed color. You will need a proof print to be sure.

[SECTION 6.4] [TABLE OF CONTENTS]

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The variety and different capabilities of graphics formats present users with a number of problems. Which one to use? Making matters worse, often each format has many variations. Specifications change over time, and implementations don't necessarily keep up with the new specs. In addition, the implementations are often incomplete or use one or more optional portions of a specification.

Of course, some formats are more popular and widely used than others. For example, TIFF files on PCs and ■ PICT files on Macs are common formats on those platforms. The longevity of your documents will be placed at risk if you choose an obscure graphics format. Inevitably, you will have to move the document to another system or document processor. At that time, you will be faced with graphics format conversion problems.

Within a project, the selection of a particular format as an internal standard is a good way to reduce problems in format conversion. For example, the computer graphics metafile (CGM) standard is used in the CALS arena to represent vector graphic images. (See Section 7-. 1. 3 CALS and . Electronic Publishing in Chapter 7 Applying Standards for more information on CALS.) Another graphics standard used to represent raster (bitmapped) images is the CCITT Group 4 format. This is otherwise know as FAX.

IGES, the Initial Graphics Exchange Specification, is another graphics standard. However, it was developed for a specific technical community Computer Aided Design (CAD). It, too, has achieved a moderate level of use in the CAD domain as the digital equivalent of blueprints. Far and away the champion of CAD interchange is AutoCAD's DXF. Because of the large installed base of AutoCad systems, it is the predominant exchange format for microcomputer based CAD systems. The main advantages of IGES are that it is not a proprietary specification and that it is often the only reasonable way to exchange information between the higherend "industrial strength" systems.

Graphics formats can be classified into three major categories: those dealing with bitmaps, those with geometrically defined objects, and those dealing with both (also known as metafiles). A graphic object means such items as lines, circles, curves, and other manipulable objects (these are often called vector graphics). The PICT format, widely used on the Macintosh, represents graphical objects. However, one of the objects is itself a bitmap, so PICT files are mixtures of bitmaps and objects.

The accompanying table, Graphics Format Characteristics, illustrates some of the characteristics of the more popular graphics formats. The column titled Native Platform indicates the original hardware platform for which the format was developeda good indication of reliable implementations.

The "na" stands for not applicable, which is true for all the "real" standards that are developed in an open, platformindependent manner.(11)

^^Graphics Format Characteristics

Name Notes type	Color or Black & White
CCITT (FAX)	bw
on
4
CGM: Computer	color
actually
Graphics Metafile
portion
DXF: Document	color
exchange
Exchange Format
widely
format
GIF	color

the

compression

HAM color

Amiga

IFF color

Amiga

IGES: Initial Graphics n/a appli

Exchange Specification cations

JPEG: Joint color

com

Photographic Experts

almost no

Group

quality

PCX color

Platform

or Both

bitmap

both

obj ects

bitmap

Mac

Fax files are based CCITT group Almost no one uses the bitmap AutoCAD's format, the most used CAD Originated on CompuServe network it has good

bitmap bitmap obj ects

Amiga

Primarily for CAD

bitmap

na Very good image

pression with loss of image PC Extremely wide use

	PCs
PICT color both Mac Mac	THE graphics format
for
	the
Mac
PNG color bitmap na image/	New graphics
format
png	generated by Web
com
	munity to be a
patent-
	free replacement
for GIF.
RASTERFILE bw bitmap na na	Based on Group 4
FAX
TARGA color bitmap PC PC	Used primarily
with
	video capture
boards
TIFF: Tagged Image color bitmap PC PC	Extremely wide
use;
File Format	too many
variations
WPG (WordPerfect) color both PC PC	File must be bitmap
or
	objects but not
both
The Tagged Image File Format (TIFF) is a widely used format for representing bitmap images. The TIFF format description of an image includes the
resolution, size, gray level or color or bi-level choices, whether dithering was performed, and what compression scheme was used. A TIFF file may
also keep a directory of images, which may correspond to all the page images of a document.
Many graphics formats use some form of data compression. Image files are large. Therefore, reliable compression is not just nice; it's a necessity.
WYSIWYG publishing systems encourage the use of more and more images, which take up more and more space. Some common compression
schemes are run length encoding (RLE), vertical replication, keyed compression (which include Huffman codes used by FAX), and Lempel-Ziv
Welch (LZW).

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Sum ¹ VH ■ hrih>r Lx|-dU lrn_pl

i■!i•■ • i -ini il»i: itatifi-r

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The Joint Photographic Experts Group (JPEG) standard is the most significant image compression standard in a long time. JPEG has caught on as a widely used image compression technology, and Web browsers are starting to support this format natively.

The company C-Cube Microsystems, a leading developer of compression hardware, has defined a standard interface to compression algorithms. Called the Image Compression Interface (ICI), this specification allows conforming software products to work with each other. Using this technique, users may pick and choose from among any number of compression algorithms.(12)

Multimedia systems, the next stage in the evolution of desktop publishing, were the motivation for the creation of these new standards (JPEG and MPEG). Coupled with hardware, these standards will provide the performance required for real-time video on the desktop. Desktop video and multimedia publishing are the next wave of new publishing technologies. Interoperability requires the development and implementation of these standards. The creation of new contentrich documents is expensive and much too valuable to be bound to any single platform.

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6 . 5 Integrating Text and Graphics

The integration of text and graphics is probably the single most problematic issue in electronic publishing. Document processing systems take many different approaches to the problems involved. Some systems import the graphics into the document. Others point to external files. Others convert the graphics into an internal format. Some allow graphics editing; others do not. Invariably, each document processing system has its own level of understanding of the graphics formats it can use. The formats themselves impose restrictions on the ultimate flexibility possible.

It is important to understand the types of graphic formats a particular document processing system can use. The portabilitythe ability to use the document on more than one computing platform of the document may depend on this one factor. Graphics formats supported on only one hardware platform will surely cause problems when the document and its associated graphics are transferred to another hardware platform.

Just as document processing systems can be classified as batch or WYSIWYG, the integration of text and graphics can also be accomplished in a batch or WYSIWYG manner. Let's examine both forms of integration and end this section with some thoughts about advice for users.

6 . 5 . 1 Language Oriented Integration

One aspect of a batch approach to text and graphics integration is a reliance on file names. In the typical case, a languageoriented document processor interprets the document and enters some graphics interpretation mode where it expects to see the file name of a graphic. The document containing the file name reference must be correct, and the file containing the graphic must also be correct and must include any conventions about the directory.

File name references are crucial when using a set of files that were moved, for example, from a UNIX to DOS system. DOS has more restrictive naming conventions then UNIX. To guarantee accurate file names, you must restrict the names to the least common denominator the DOS file names. An alternative approach to restrictive file names is to come up with a file name mapping scheme with some utility programs to automate the process. Either way, the solution is distasteful.

Encapsulated PostScript (EPS) files are the most commonly used format to represent the graphics placed in documents. Virtually all electronic publishing systems, including both the batch and WYSIWYG systems, allow the user to place an EPS file (13).

Both TeX and troff have mechanisms for importing PostScript files. These mechanisms . consist of a ■ set of TeX commands or troff macros, that insert the PostScript graphic at the appropriate point in the document. . . .

A marvelous example of text and graphics integration in the UNIX environment is FaceSaver.(14) It's also an example of the UNIX hacker mentality. Over a period of . several years, attendees of USENIX conferences ■ (a popular' UNIX conference) had their pictures taken and saved by the people running the FaceSaver project.' The idea was to ■ create a repository of faces accessible on the Internet. This has now been accomplished and the faces are stored at UUNET, a widely accessible Internet provider.

k •. •. k .

Given the existence of this repository of images, it is only natural that a number of ■ "FaceSaver" utilities ■ have been created: One particularly clever set converts the image into PostScript and enables the user ' to create business cards, labels, a letterhead, or a dartboard.(15) . .

6 . 5 . 2 WYSIWYG Integration

Some document processing systems, usually the higherend systems, attempt to display the graphic on the screen with the text. The manipulation of these graphics varies widely, ■ ranging from no manipulation to total control. One important characteristic is whether the graphics are treated as an unbreakable block or whether the system supports some amount of graphic editing. In addition, some systems have an internal set of graphics. For example, FrameMaker has, roughly put, the equivalent to MacDraw built in, but without bitmapped image manipulation capabilities.

The placement of graphics and how the graphics should flow, visually and logically, within the text is a major design issue for page layout and document processing systems. The classic page layout system typified by PageMaker allows a high degree of textual integration with the graphics. You simply drag the graphic into an area of text, and the system will visually flow the text around the graphic. The control of such run-arounds gives the document designer a great deal of freedom. (See Section 3. 1. 4 Page in Chapter 3 Points of View for an illustration of text flowing around a graphic.)

Some systems allow graphics to be anchored to text; as new text is inserted or deleted, the graphic remains attached to the correct place in the text. Another form of anchoring is to attach the graphic to a particular location on a page, such - as the top of the page.

WYSIWYG publishing systems differ in many subtle ways. The ability of a system to incorporate graphics into an integrated document is an area in which these differences can make a real difference in your publishing job. Keep an eye out for the types of graphic manipulations allowed and how the system handles external file references.

6 . 5 . 3 Inline versus External on the Web

As we've just concluded our discussion of language versus WYSIWYG, it is appropriate to compare the two integration mechanisms available for Web browsing. In much the same way that document processing systems have evolved from languages to WYSIWYG, Web browsers are evolving from a collection of loosely integrated "helper" applications to tighter integrated inline systems.

Lost in all the technical whiz-bang demos and slick Web pages we see is the supremely important issue of the user interface. The most significant problem with the external helper application approach is the change in user interface that a user must endure. One second you're happily clicking on links and the next moment some foreign application pops up and you must figure out what to do. Of course, the use of external applications is

a good way of distributing new types of data formats before going through the labor of integrating that data type with your browser.

Netscape appears to have a good solution to this problem with the development of an API (16) that formalizes how applications may embed themselves in Web documents. This approach is similar to Microsoft's OLE (Object Linking and Embedding)(17) and the OpenDoc(18) architecture. The concept of "plug-ins," dynamically callable functional additions to an application, is well proven and is used extensively by a wide variety of PC and Mac software vendors. In geek terms, the plug-in architectures really consist of a welldefined Application Programming Interface (API), the interface between an application and externally defined functionality. The first Netscape Plug-in was a Virtual Reality Modeling Language (VRML) browser called WebFX by Paper Software Inc. In fact Netscape liked it so much they bought the company!(19) The plug-in is now called Live3D.

An example at the Live3D simple examples page at Netscape

This particular plug-in example uses the "frames" extension defined by Netscape that allows independently scrollable windows within the context of a single Web "page."

One interesting example of Web application integration is Adobe's Acrobat Amber. It effectively embeds their PDF Reader product into the Web browser. It functions quite nicely, but again, the integration of user interfaces becomes problematic. The icons from the Acrobat Reader product are now presently embedded on top of the PDF page in a strange location for Netscape's Navigator. It is unusual to go to a URL and have another application effectively embed itself in the page. Not terrible, just unusual.