| As color printers and scanners grow in popularity, users
face the challenge of maintaining color fidelity
throughout the tricky process of importing an image,
modifying it on the screen, and rendering it on a printer.
All too often, the result is a disappointment: off-balance
color, harsh or weak contrast, too dark or too light. The
main problem is the wide variation of color accuracy among
input devices, color monitors, and output devices. In the
world of desktop color, what you see is rarely what you
get. Users need a color management system that knows the
characteristics of all devices in the process and can
automatically compensate for their vagaries. Some desktop publishing programs, such as QuarkXPress, Photoshop, PhotoStyler, and CorelDraw, offer their own color management systems, usually licensed from other companies. But these systems are not always compatible with each other, and people who use several programs must deal with several different mechanisms. Apple addressed this problem on the Macintosh in 1993 by introducing ColorSync, an open-architecture color management extension for System 7. ColorSync defined a file format for profiles that record the attributes of input devices, monitors, and output devices. Vendors can ship calibrated profiles with their devices, and programs can apply those profiles to maintain consistent quality during color-space conversions and other transformations. With the release of Chicago, Microsoft is not only building a similar framework into its own system software, it's also cooperating with Apple and other vendors to support a standard profile format that works across multiple platforms. The result is the first industry-standard color management system for desktop publishing. Chicago's color management architecture is called the Image Color Matching Framework (usually abbreviated ICM), a library of about 16 new API routines that are callable from any Chicago application. Another component is the Kodak Color Matching Module, a color management engine licensed from Eastman Kodak (Rochester, NY). It's the same engine already included with Adobe Photoshop and Aldus PhotoStyler and scheduled for inclusion with the next release of Aldus PageMaker. In Chicago, both ICM and the Kodak color engine are contained in a DLL called ICM32.DLL that will occupy about 224 KB in the WINDOWS\SYSTEM directory. "It's basically a way of keeping the drivers and the applications from having to build in their own color management features," says Myron Kassaraba, director of licensing and market development for Kodak. Developers still have to modify their applications to take advantage of ICM, he notes, but the availability of color management in the operating system will save them a lot of trouble. Chicago's color profiles will conform to the InterColor Profile Format, which was recently defined by the InterColor Consortium. Members include Adobe, Agfa, Apple, Kodak, Microsoft, Silicon Graphics, Sun, and Taligent. The standardized profiles will be compatible with Apple's ColorSync 2.0 and with a future version of SunSoft's Solaris. ICM also supports the new Plug and Play specifications for video monitors recently adopted by VESA (Video Electronics Standards Association). These specifications define a back channel that allows monitors to pass information back to the computer along the video cable, thus providing an avenue for auto-calibration. For the most critical applications, however, users still need to calibrate their screens with a spectrophotometer or colorimeter to compensate for such factors as the color shift of the CRT over time. For instance, X-Rite (Grandville, MI) is introducing a color-calibration solution called RiteColor Pro that works with both ICM in Chicago and ColorSync on the Mac. The $2995 package includes a reflective color test chart for scanners, two colorimeters (one for measuring the screen and another for measuring hard-copy output), and a program that analyzes the meter readings to create the InterColor-compliant custom profiles. RiteColor Pro compensates for such factors as manufacturing variations in monitors, different kinds of printer paper, and slight differences in the color of refilled ink-jet cartridges. InterColor profiles can store a wealth of information about scanners, monitors, printers, color fax machines, film recorders, imagesetters, and other devices. For example, if you import Photo CD images, the profile may vary according to the type of film that was scanned onto the CD: Kodak Ektachrome has slightly different characteristics than Kodachrome. The profiles also contain information that aids color-space conversions, such as YCC to RGB (which is required to display a Photo CD image on a monitor) or RGB to CMYK (typically encountered when sending an image to a printer). Image file formats such as TIFF and GIF may be redefined to include similar data. "Right now, when you load an RGB image such as a TIFF file, you have no idea what references were used when it was created," says Kassaraba. "It might have been created on a system with a completely different gamma and everything else." This problem is readily apparent when moving some kinds of image files between Macs and PCs. Macintosh images often look too dark on PCs, and PC images often look washed out on Macs. The usual solution is to manually alter the gamma curve with an image editor such as Photoshop, but that adjustment could happen automatically if image files were tagged with gamma values according to a standard format. A program could read those values while importing the file and call SetDisplayGammaRamp, a gamma-correction function in Chicago's ICM API that is absent from Windows 3.1 (the Macintosh Toolbox has a similar QuickDraw function, called SetDeviceAttribute). Since most existing devices don't have color profiles yet, Chicago will come with a database of popular monitors and graphics cards. You can access this database from the Desktop Property Sheet and pick from a scrolling list. If you don't have a program that's been upgraded to support ICM, try the new Paintbrush accessory. By the time Chicago is released, there is a good chance Paintbrush will be ICM-aware, according to Microsoft's Chicago core program manager George Moore. And since Paintbrush is an OLE server, Moore notes, you could embed it in applications that do not support ICM and still reap some benefits of hassle-free color management. ICM's open architecture also lets users install different color management engines that override the Kodak engine included with Chicago. For example, Pantone (Carlstadt, NJ) has a new version of its POCE (Pantone Open Color Environment) that is compatible with both ICM and ColorSync 2.0. POCE is the only engine that addresses Pantone colors, which are widely used in the publishing industry. Richard Herbert, vice president of Pantone's Electronic Color Systems, says POCE is licensed for free to developers, who can bundle it with their Chicago and Macintosh programs. A standardized approach to color management will strengthen Microsoft's bid to challenge the supremacy of the Macintosh in professional desktop publishing. But it will also make life easier for users, whether they prefer Chicago, the Macintosh, or any other platform that adopts the InterColor format. Illustration: Chicago's Image Color Matching Framework. Chicago's device-independent color architecture, or Image Color Matching Framework, consists of 16 new API calls, a color management engine (the Kodak Color Matching Module, which can be replaced by other engines), and device profiles that adhere to the InterColor Profile Format. Applications call on ICM to map colors between the physical color spaces of input and output devices, thus maintaining more consistent color throughout the process of scanning, viewing, and printing. Illustration: Color Printer Sales in North America. Market research firm Dataquest predicts strong growth in sales of color printers, increasing from about 13 percent of the market in 1992 to nearly 34 percent in 1996. Illustration: Page Scanner Sales in North America. Color page scanners are steadily growing in popularity, although research firm Dataquest predicts a strong surge in monochrome scanners due to rapidly dropping prices. Tom R. Halfhill is a BYTE senior news editor based in San Mateo, California. You can reach him on the Internet or BIX at thalfhill@ bix.com. Copyright 1994-1998 BYTE |