Henceforth, the graphic coordinate system for a track is referred to simply as its coordinate system . The media handler associated with the track's media is responsible for displaying an image into this rectangle. This process is shown in Figure 0-23. Both the track matte and the track clipping region are optional. A track matte provides a mechanism for mixing images.
Mattes contain several bits per pixel and are defined in the track's coordinate system.
The matte can be used to perform a deep-mask operation on the image in the track rectangle. The Movie Toolbox displays the weighted average of the track and its destination based on the corresponding pixel value in the matte. The track clipping region is a QuickDraw region that defines a portion of the track rectangle to retain. The track clipping region is defined in the track's coordinate system. This clipping operation creates the track boundary region, which is the intersection of the track rectangle and the track clipping region .