Programming With QuickTime Sprites

Sprites' Four Corners

Some sprite actions and operands refer to a sprite's "four corners." These four corners are expressed in its track's local coordinate system. They are the points derived by taking the four corners of the sprite's source box and applying the current image's registration point and the sprite's source matrix. The first corner is the top-left, the second corner is the top-right, the third corner is the bottom right, and the fourth corner is the bottom-left.

Figure 0-4 shows a rotated bounding box in a sprite track's local coordinate system.

Figure 4 The rotated bounding box becomes the sprite four corners