Specifications

CHAPTER 3
Application Program Interface
VPTEngine Component 35
Kelvin 3
This data type represents Kelvin degrees, a simple unit of measuring a very narrow
range of colors.
typedef long Kelvin;
VPTGamma 3
This data structure is used by the VPTEngine component to represent a gamma table. A
gamma curve defines the relationship between the color intensity (chrominance) of the
screen and the light intensity (luminance) of the screen. With a low gamma curve, colors
may look washed out to the user, while a high gamma curve provides more contrast. The
human eye can determine subtle changes in color, but does not register these changes in
a linear way. Color systems are linear and continuous. A linear gamma curve ensures
that the display produces the correct luminance levels on each primary color channel,
and matches the user’s nonlinear color expectations to the display’s linear color devices.
typedef struct VPTGamma
{
unsigned shortred[256];
unsigned shortgreen[256];
unsigned shortblue[256];
} VPTGamma, *VPTGammaPtr, **VPTGammaHdl;
red, green, blue
Arrays containing the gamma curve for each electron gun of the
display.
VPTEngine Component Functions 3
This section describes the VPTEngine components functions associated with
■ calibration
■ white-point settings
■ ambient-light settings
■ gamma-curve settings
■ color gamut identification
■ translating standard RGB QuickDraw colors to Tristimulus color values, and vice
versa