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Inside Macintosh: QuickDraw GX Environment and Utilities /

Chapter 7 - QuickDraw GX Stream Format / QuickDraw GX Stream Format Reference

Ink Object Omit Byte Constants and Data Types

Colors Omit Byte Masks and Shifts

The gxOmitColorsMask enumeration defines which bits in an omit byte correspond to the data compression opcode for the field descriptors in the gxColor structure. The sequence of data is also defined. The omit byte and its related data sequence is given in the section "Color Data" beginning on page 7-44.

enum gxOmitColorsMask {
   gxOmitColorsSpaceMask      = 0xC0,
   gxOmitColorsProfileMask    = 0x30,
   gxOmitColorsComponentsMask = 0x0F,
   gxOmitColorsIndexMask      = 0x0C,
   gxOmitColorsIndexSetMask   = 0x03
};

Constant descriptions

gxOmitColorsSpaceMask

The mask used to select the data compression bits for the space field descriptor.

gxOmitColorsProfileMask

The mask used to select the data compression bits for the profile field descriptor.

gxOmitColorsComponentsMask

The mask used to select the data compression bits for the element.component[4] field descriptor.

gxOmitColorsIndexMask

The mask used to select the data compression bits for the element.indexed.index field descriptor.

gxOmitColorsIndexSetMask

The mask used to select the data compression bits for the element.index.Set field descriptor.

Once one of the gxOmitColorsMask enumeration masks has been used to select a data compression opcode for a field descriptor in the gxColor structure, the corresponding bit shift from the gxOmitColorsShift enumeration can be applied to the selected bits. The selected bits must be moved to the right by the indicated number of bits to isolate the data compression opcode so that it can be compared to other values.

enum gxOmitColorsShift {
   gxOmitColorsSpaceShift        = 6,
   gxOmitColorsProfileShift      = 4,
   gxOmitColorsComponentsShift   = 0,
   gxOmitColorsIndexShift        = 2,
   gxOmitColorsIndexSetShift     = 0
};

Constant descriptions

gxOmitColorsSpaceShift

The bit shift required to isolate the compression bits for the space field descriptor.

gxOmitColorsProfileShift

The bit shift required to isolate the compression bits for the profile field descriptor.

gxOmitColorsComponentsShift

The bit shift required to isolate the compression bits for the element.component[4] field descriptor.

gxOmitColorsIndexShift

The bit shift required to isolate the compression bits for the element.indexed.index field descriptor.

gxOmitColorsIndexSetShift

The bit shift required to isolate the compression bits for the element.indexed.set field descriptor.