7.9 Device-independent Color and Xcms

As already described, the X server supports a color name database in order to translate textual color names into intensity values for the red, green, and blue primaries. This is a convenience for users and a simple attempt at device-independent color—if server vendors tune the database to the particular displays they support, then applications that use the standard named colors can be confident that those colors will appear the same across all displays.

In practice, however, the color database has not been tuned for most displays. Furthermore, there are a growing number of visualization and other applications that use color and shading to display data and convey information rather than simply as decoration. These applications need the ability to precisely specify device-independent colors and often to divide a range of colors into perceptually equal intervals. A small number of hand-tuned named colors in a database is simply not adequate. X11R5 addresses these needs with Xcms, the X Color Management System, which was developed primarily by Tektronix for the X Consortium.

Xcms includes:

  • A new standard textual representation for device-independent color strings.

  • Modifications to several existing Xlib functions to support this new standard representation.

  • The provision for a database that maps color names to device-independent color specifications. This database is read by Xlib rather than by the X server.

  • The Xcms API—a new set of Xlib functions that ...

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