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Specifying Colors for Use on TV

Computer-generated colors often differ in appearance when viewed on a television video monitor rather than on a computer video monitor. The analog, NTSC, signal that is used in televisions has limitations and unique characteristics. Colors generated on the computer need to be carefully previewed, reviewed, and electronically tested before use on a television video monitor.

In the TrafficChannel.exe program, as in most computer implementations, color is specified by quantitatively mixing the colors red, green, and blue. That is an RGB color system. The desired amount of each color is specified as a quantity from 0 to 255. For example, pure red would be specified as 255 0.

In general, the range of possible colors is smaller for the television than for the computer. When the computer generates a color that is outside the television's display range capabilities, there will be artifacts such as aliasing, color wash out, and elements shadowing displayed on the television.

The following "Rules of Thumb" can be used for specifying safe colors:

The above list is a conservative starting point. There can be exceptions, but always verify your selection with a video monitoring instrument.

The Traffic Channel application supports up to 16 colors as specified in the Color Table Definition section of the map configuration file. All elements on the display - banners, static regions, segments, and image file decorations - must contain only colors available in this palette.

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(May 11, 1998)