Developer Documentation

QuickTime 4 API Documentation

3D Graphics Programming with QuickDraw 3D 1.5.4

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Buffer Compositing Modes

A drawing engine may support a buffer compositing mode that determines how the drawing engine composites generated pixels with the initial contents of the drawing buffer. You specify an engine's buffer compositing mode by assigning a value to its kQATag_BufferComposite state variable. The default value of this variable for a drawing engine that supports buffer compositing is kQABufferComposite_None . You can use the following constants to specify a buffer compositing mode.

#define kQABufferComposite_None                     0
#define kQABufferComposite_PreMultiply              1
#define kQABufferComposite_Interpolate              2

Constant descriptions

kQABufferComposite_None
The drawing engine performs no compositing. Newly generated pixels overwrite the initial contexts of the buffer.
kQABufferComposite_PreMultiply
The drawing engine composites new pixels with existing pixels by premulitplying their color components.
kQABufferComposite_Interpolate
The drawing engine composites new pixels with existing pixels by interpolating their color components.

© 1997 Apple Computer, Inc.

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