Color management

Color management is a technology to calibrate the color of input devices (e.g., scanners or digital cameras), display devices and output devices (e.g., printers or offset presses). Parts of this technology are implemented in the operating system (OS), the API or directly in the application.

A major concept in color management is the working space. This describes a color space, which is not connected to a special device. The most commonly used working space is sRGB. The concept for color management in Microsoft Windows and Microsoft Office products is that every driver for an input device makes a color transformation from the color space of the device to sRGB. For the output device or the monitor, the driver has to make a color transformation from sRGB to the color space of the output device. This kind of implementation of color management is very user-friendly, because there is no need for any configuration. But the quality of the results depends entirely on the quality of the color transformations, which are part of the drivers. A more open concept of color management is the use of an ICC-compatible color management system. The International Color Consortium (ICC) is an industry consortium, which has defined an open standard for a Color Matching Module (CMM) at the OS level, and color profiles (ICC profiles) for the devices and the working space. Another ICC concept is to make color profiles a part of file formats like TIFF, JPEG, EPS, PDF, and SVG.

A clear implementation of color management in the user interface of the OS would have the selection of profiles for monitors and for the working space in system configuration, and the selection of device profiles in the scanner or printer driver. Analyzing the actual implementation of color management at the level of the OS, the drivers, and the applications shows that there is substantial confusion about color management at the side of the software architects for operating systems and the software developers of drivers and applications. Actual problems include:

• There is often no clear concept of the software architects of the OS on how to implement color mangement at the OS level, including guidelines for the developers of applications and drivers on how to use the color management possibilties of the OS.
  • There is not the concept of a choosable working space and a monitor profile in the graphics architecture and in the window system of the OS. On Mac OS this is possible, but nearly all applications ignore it.
  • The OS architecture for printer drivers doesn't allow the configuration of profiles for a working space and a device space.
• Some important file formats like EPS are incompatible for color management on the host computer. For color matching of EPS files, a PostScript RIP is necessary.
• Color mangement for the printer is sometimes implemented on different levels such as in the application, on the OS driver Level, or in the PostScript RIP. This can cause double or triple color matching with unwanted results.

References

• Adams, Richard M. & Weisberg, Joshua B. The GATF Practical Guide to Color Management. ISBN 0-883-62248-3
• Field, Gary. Color and Its Reproduction. ISBN 0-883-62407-9
• Fraser, Bruce; Murphy, Chris; & Bunting, Fred. Real World Color Management. ISBN 0-201-77340-6
• Sharma, Abhay. Understanding Color Management. ISBN 1-401-81447-6

External links

More information about color management for software developers can be found here:

• ICC profile specification (http://www.color.org/icc_specs2.html)
• Overview of color management in Microsoft Windows (http://www.microsoft.com/whdc/device/display/color/default.mspx)
• Mac OS X and ColorSync (http://developer.apple.com/technotes/tn/tn2035.html)
• Basic color management for X (http://software.newsforge.com/article.pl?sid=05/03/08/1712218) on Linux systems
  • LittleCMS (http://www.littlecms.com/) - Free, open source color management engine
• www.coloraid.de, includes open source color management tools
• Datacolor - Color Management Solutions (http://www.datacolor.com)
• Color Management Systems Lab (http://www.rit.edu/~rycppr/) at the Rochester Institute of Technologyde:Farbmanagement