unsigned long ColorTranslate(void *pvDisplayData,
                     unsigned long ulRGBColor);

The higher-level graphics driver APIs make use of a standard 24-bit RGB color description with the color described in a single, unsigned long value with the red component in bits 16 to 23, green in bits 8 to 15, and blue in bits 0 to 7. Different displays, however, describe color in different ways so the ColorTranslate function allows the graphics library to obtain a representation of a given RGB24 color in the native format supported by the display.

For monochrome displays, the returned value should represent the brightness of the supplied RGB color. For color displays, the returned value should represent the original color as closely as possible given the constraints of the display. If the display supports 16-bit RGB, for example, the returned color value truncates, masks, and shifts the supplied 8-bit R,G, and B samples into a correctly packed 16-bit value.

All other calls to the display driver will be passed pre-translated colors which are colors that have been returned from a previous call to the ColorTranslate function, so the overhead of color translation is kept to a minimum.